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Java Android: how to compare current time to a calculated time? [duplicate]

I'm using Java's java.util.Date class in Scala and want to compare a Date object and the current time. I know I can calculate the delta by using getTime():
(new java.util.Date()).getTime() - oldDate.getTime()
However, this just leaves me with a long representing milliseconds. Is there any simpler, nicer way to get a time delta?

Simple diff (without lib)
/**
* Get a diff between two dates
* #param date1 the oldest date
* #param date2 the newest date
* #param timeUnit the unit in which you want the diff
* #return the diff value, in the provided unit
*/
public static long getDateDiff(Date date1, Date date2, TimeUnit timeUnit) {
long diffInMillies = date2.getTime() - date1.getTime();
return timeUnit.convert(diffInMillies,TimeUnit.MILLISECONDS);
}
And then can you call:
getDateDiff(date1,date2,TimeUnit.MINUTES);
to get the diff of the 2 dates in minutes unit.
TimeUnit is java.util.concurrent.TimeUnit, a standard Java enum going from nanos to days.
Human readable diff (without lib)
public static Map<TimeUnit,Long> computeDiff(Date date1, Date date2) {
long diffInMillies = date2.getTime() - date1.getTime();
//create the list
List<TimeUnit> units = new ArrayList<TimeUnit>(EnumSet.allOf(TimeUnit.class));
Collections.reverse(units);
//create the result map of TimeUnit and difference
Map<TimeUnit,Long> result = new LinkedHashMap<TimeUnit,Long>();
long milliesRest = diffInMillies;
for ( TimeUnit unit : units ) {
//calculate difference in millisecond
long diff = unit.convert(milliesRest,TimeUnit.MILLISECONDS);
long diffInMilliesForUnit = unit.toMillis(diff);
milliesRest = milliesRest - diffInMilliesForUnit;
//put the result in the map
result.put(unit,diff);
}
return result;
}
http://ideone.com/5dXeu6
The output is something like Map:{DAYS=1, HOURS=3, MINUTES=46, SECONDS=40, MILLISECONDS=0, MICROSECONDS=0, NANOSECONDS=0}, with the units ordered.
You just have to convert that map to a user-friendly string.
Warning
The above code snippets compute a simple diff between 2 instants. It can cause problems during a daylight saving switch, like explained in this post. This means if you compute the diff between dates with no time you may have a missing day/hour.
In my opinion the date diff is kind of subjective, especially on days. You may:
count the number of 24h elapsed time: day+1 - day = 1 day = 24h
count the number of elapsed time, taking care of daylight savings: day+1 - day = 1 = 24h (but using midnight time and daylight savings it could be 0 day and 23h)
count the number of day switches, which means day+1 1pm - day 11am = 1 day, even if the elapsed time is just 2h (or 1h if there is a daylight saving :p)
My answer is valid if your definition of date diff on days match the 1st case
With JodaTime
If you are using JodaTime you can get the diff for 2 instants (millies backed ReadableInstant) dates with:
Interval interval = new Interval(oldInstant, new Instant());
But you can also get the diff for Local dates/times:
// returns 4 because of the leap year of 366 days
new Period(LocalDate.now(), LocalDate.now().plusDays(365*5), PeriodType.years()).getYears()
// this time it returns 5
new Period(LocalDate.now(), LocalDate.now().plusDays(365*5+1), PeriodType.years()).getYears()
// And you can also use these static methods
Years.yearsBetween(LocalDate.now(), LocalDate.now().plusDays(365*5)).getYears()

The JDK Date API is horribly broken unfortunately. I recommend using Joda Time library.
Joda Time has a concept of time Interval:
Interval interval = new Interval(oldTime, new Instant());
EDIT: By the way, Joda has two concepts: Interval for representing an interval of time between two time instants (represent time between 8am and 10am), and a Duration that represents a length of time without the actual time boundaries (e.g. represent two hours!)
If you only care about time comparisions, most Date implementations (including the JDK one) implements Comparable interface which allows you to use the Comparable.compareTo()

int diffInDays = (int)( (newerDate.getTime() - olderDate.getTime())
/ (1000 * 60 * 60 * 24) )
Note that this works with UTC dates, so the difference may be a day off if you look at local dates. And getting it to work correctly with local dates requires a completely different approach due to daylight savings time.

Using the java.time framework built into Java 8+:
ZonedDateTime now = ZonedDateTime.now();
ZonedDateTime oldDate = now.minusDays(1).minusMinutes(10);
Duration duration = Duration.between(oldDate, now);
System.out.println("ISO-8601: " + duration);
System.out.println("Minutes: " + duration.toMinutes());
Output:
ISO-8601: PT24H10M
Minutes: 1450
For more info, see the Oracle Tutorial and the ISO 8601 standard.

tl;dr
Convert your obsolete java.util.Date objects to their replacement, java.time.Instant. Then calculate the elapsed time as a Duration.
Duration d =
Duration.between( // Calculate the span of time between two moments as a number of hours, minutes, and seconds.
myJavaUtilDate.toInstant() , // Convert legacy class to modern class by calling new method added to the old class.
Instant.now() // Capture the current moment in UTC. About two and a half hours later in this example.
)
;
d.toString(): PT2H34M56S
d.toMinutes(): 154
d.toMinutesPart(): 34
ISO 8601 Format: PnYnMnDTnHnMnS
The sensible standard ISO 8601 defines a concise textual representation of a span of time as a number of years, months, days, hours, etc. The standard calls such such a span a duration. The format is PnYnMnDTnHnMnS where the P means "Period", the T separates the date portion from the time portion, and in between are numbers followed by a letter.
Examples:
P3Y6M4DT12H30M5Sthree years, six months, four days, twelve hours, thirty minutes, and five seconds
PT4H30MFour and a half hours
java.time
The java.time framework built into Java 8 and later supplants the troublesome old java.util.Date/java.util.Calendar classes. The new classes are inspired by the highly successful Joda-Time framework, intended as its successor, similar in concept but re-architected. Defined by JSR 310. Extended by the ThreeTen-Extra project. See the Tutorial.
Moment
The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).
Instant instant = Instant.now() ; // Capture current moment in UTC.
Best to avoid the legacy classes such as Date/Calendar. But if you must inter-operate with old code not yet updated to java.time, convert back and forth. Call new conversion methods added to the old classes. For moving from a java.util.Date to an Instant, call Date::toInstant.
Instant instant = myJavaUtilDate.toInstant() ; // Convert from legacy `java.util.Date` class to modern `java.time.Instant` class.
Span of time
The java.time classes have split this idea of representing a span of time as a number of years, months, days, hours, minutes, seconds into two halves:
Period for years, months, days
Duration for days, hours, minutes, seconds
Here is an example.
ZoneId zoneId = ZoneId.of ( "America/Montreal" );
ZonedDateTime now = ZonedDateTime.now ( zoneId );
ZonedDateTime future = now.plusMinutes ( 63 );
Duration duration = Duration.between ( now , future );
Dump to console.
Both Period and Duration use the ISO 8601 standard for generating a String representation of their value.
System.out.println ( "now: " + now + " to future: " + now + " = " + duration );
now: 2015-11-26T00:46:48.016-05:00[America/Montreal] to future: 2015-11-26T00:46:48.016-05:00[America/Montreal] = PT1H3M
Java 9 adds methods to Duration to get the days part, hours part, minutes part, and seconds part.
You can get the total number of days or hours or minutes or seconds or milliseconds or nanoseconds in the entire Duration.
long totalHours = duration.toHours();
In Java 9 the Duration class gets new methods for returning the various parts of days, hours, minutes, seconds, milliseconds/nanoseconds. Call the to…Part methods: toDaysPart(), toHoursPart(), and so on.
ChronoUnit
If you only care about a simpler larger granularity of time, such as “number of days elapsed”, use the ChronoUnit enum.
long daysElapsed = ChronoUnit.DAYS.between( earlier , later );
Another example.
Instant now = Instant.now();
Instant later = now.plus( Duration.ofHours( 2 ) );
…
long minutesElapsed = ChronoUnit.MINUTES.between( now , later );
120
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8 and SE 9 and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
Joda-Time
UPDATE: The Joda-Time project is now in maintenance mode, with the team advising migration to the java.time classes. I leave this section intact for history.
The Joda-Time library uses ISO 8601 for its defaults. Its Period class parses and generates these PnYnMnDTnHnMnS strings.
DateTime now = DateTime.now(); // Caveat: Ignoring the important issue of time zones.
Period period = new Period( now, now.plusHours( 4 ).plusMinutes( 30));
System.out.println( "period: " + period );
Renders:
period: PT4H30M

You need to define your problem more clearly. You could just take the number of milliseconds between the two Date objects and divide by the number of milliseconds in 24 hours, for example... but:
This won't take time zones into consideration - Date is always in UTC
This won't take daylight saving time into consideration (where there can be days which are only 23 hours long, for example)
Even within UTC, how many days are there in August 16th 11pm to August 18th 2am? It's only 27 hours, so does that mean one day? Or should it be three days because it covers three dates?

Days d = Days.daysBetween(startDate, endDate);
int days = d.getDays();
https://www.joda.org/joda-time/faq.html#datediff

A slightly simpler alternative:
System.currentTimeMillis() - oldDate.getTime()
As for "nicer": well, what exactly do you need? The problem with representing time durations as a number of hours and days etc. is that it may lead to inaccuracies and wrong expectations due to the complexity of dates (e.g. days can have 23 or 25 hours due to daylight savings time).

Using millisecond approach can cause problems in some locales.
Lets take, for example, the difference between the two dates 03/24/2007 and 03/25/2007 should be 1 day;
However, using the millisecond route, you'll get 0 days, if you run this in the UK!
/** Manual Method - YIELDS INCORRECT RESULTS - DO NOT USE**/
/* This method is used to find the no of days between the given dates */
public long calculateDays(Date dateEarly, Date dateLater) {
return (dateLater.getTime() - dateEarly.getTime()) / (24 * 60 * 60 * 1000);
}
Better way to implement this is to use java.util.Calendar
/** Using Calendar - THE CORRECT WAY**/
public static long daysBetween(Calendar startDate, Calendar endDate) {
Calendar date = (Calendar) startDate.clone();
long daysBetween = 0;
while (date.before(endDate)) {
date.add(Calendar.DAY_OF_MONTH, 1);
daysBetween++;
}
return daysBetween;
}

Since all the answers here are correct but use legacy java or 3rd party libs like joda or similar, I will just drop another way using new java.time classes in Java 8 and later. See Oracle Tutorial.
Use LocalDate and ChronoUnit:
LocalDate d1 = LocalDate.of(2017, 5, 1);
LocalDate d2 = LocalDate.of(2017, 5, 18);
long days = ChronoUnit.DAYS.between(d1, d2);
System.out.println( days );

There are many ways you can find the difference between dates & times. One of the simplest ways that I know of would be:
Calendar calendar1 = Calendar.getInstance();
Calendar calendar2 = Calendar.getInstance();
calendar1.set(2012, 04, 02);
calendar2.set(2012, 04, 04);
long milsecs1= calendar1.getTimeInMillis();
long milsecs2 = calendar2.getTimeInMillis();
long diff = milsecs2 - milsecs1;
long dsecs = diff / 1000;
long dminutes = diff / (60 * 1000);
long dhours = diff / (60 * 60 * 1000);
long ddays = diff / (24 * 60 * 60 * 1000);
System.out.println("Your Day Difference="+ddays);
The print statement is just an example - you can format it, the way you like.

If you don't want to use JodaTime or similar, the best solution is probably this:
final static long MILLIS_PER_DAY = 24 * 3600 * 1000;
long msDiff= date1.getTime() - date2.getTime();
long daysDiff = Math.round(msDiff / ((double)MILLIS_PER_DAY));
The number of ms per day is not always the same (because of daylight saving time and leap seconds), but it's very close, and at least deviations due to daylight saving time cancel out over longer periods. Therefore dividing and then rounding will give a correct result (at least as long as the local calendar used does not contain weird time jumps other than DST and leap seconds).
Note that this still assumes that date1 and date2 are set to the same time of day. For different times of day, you'd first have to define what "date difference" means, as pointed out by Jon Skeet.

Subtracting the dates in milliseconds works (as described in another post), but you have to use HOUR_OF_DAY and not HOUR when clearing the time parts of your dates:
public static final long MSPERDAY = 60 * 60 * 24 * 1000;
...
final Calendar dateStartCal = Calendar.getInstance();
dateStartCal.setTime(dateStart);
dateStartCal.set(Calendar.HOUR_OF_DAY, 0); // Crucial.
dateStartCal.set(Calendar.MINUTE, 0);
dateStartCal.set(Calendar.SECOND, 0);
dateStartCal.set(Calendar.MILLISECOND, 0);
final Calendar dateEndCal = Calendar.getInstance();
dateEndCal.setTime(dateEnd);
dateEndCal.set(Calendar.HOUR_OF_DAY, 0); // Crucial.
dateEndCal.set(Calendar.MINUTE, 0);
dateEndCal.set(Calendar.SECOND, 0);
dateEndCal.set(Calendar.MILLISECOND, 0);
final long dateDifferenceInDays = ( dateStartCal.getTimeInMillis()
- dateEndCal.getTimeInMillis()
) / MSPERDAY;
if (dateDifferenceInDays > 15) {
// Do something if difference > 15 days
}

Take a look at Joda Time, which is an improved Date/Time API for Java and should work fine with Scala.

int daysDiff = (date1.getTime() - date2.getTime()) / MILLIS_PER_DAY;

Let me show difference between Joda Interval and Days:
DateTime start = new DateTime(2012, 2, 6, 10, 44, 51, 0);
DateTime end = new DateTime(2012, 2, 6, 11, 39, 47, 1);
Interval interval = new Interval(start, end);
Period period = interval.toPeriod();
System.out.println(period.getYears() + " years, " + period.getMonths() + " months, " + period.getWeeks() + " weeks, " + period.getDays() + " days");
System.out.println(period.getHours() + " hours, " + period.getMinutes() + " minutes, " + period.getSeconds() + " seconds ");
//Result is:
//0 years, 0 months, *1 weeks, 1 days*
//0 hours, 54 minutes, 56 seconds
//Period can set PeriodType,such as PeriodType.yearMonthDay(),PeriodType.yearDayTime()...
Period p = new Period(start, end, PeriodType.yearMonthDayTime());
System.out.println(p.getYears() + " years, " + p.getMonths() + " months, " + p.getWeeks() + " weeks, " + p.getDays() + "days");
System.out.println(p.getHours() + " hours, " + p.getMinutes() + " minutes, " + p.getSeconds() + " seconds ");
//Result is:
//0 years, 0 months, *0 weeks, 8 days*
//0 hours, 54 minutes, 56 seconds

If you need a formatted return String like
"2 Days 03h 42m 07s", try this:
public String fill2(int value)
{
String ret = String.valueOf(value);
if (ret.length() < 2)
ret = "0" + ret;
return ret;
}
public String get_duration(Date date1, Date date2)
{
TimeUnit timeUnit = TimeUnit.SECONDS;
long diffInMilli = date2.getTime() - date1.getTime();
long s = timeUnit.convert(diffInMilli, TimeUnit.MILLISECONDS);
long days = s / (24 * 60 * 60);
long rest = s - (days * 24 * 60 * 60);
long hrs = rest / (60 * 60);
long rest1 = rest - (hrs * 60 * 60);
long min = rest1 / 60;
long sec = s % 60;
String dates = "";
if (days > 0) dates = days + " Days ";
dates += fill2((int) hrs) + "h ";
dates += fill2((int) min) + "m ";
dates += fill2((int) sec) + "s ";
return dates;
}

After wading through all the other answers, to keep the Java 7 Date type but be more precise/standard with the Java 8 diff approach,
public static long daysBetweenDates(Date d1, Date d2) {
Instant instant1 = d1.toInstant();
Instant instant2 = d2.toInstant();
long diff = ChronoUnit.DAYS.between(instant1, instant2);
return diff;
}

Note: startDate and endDates are -> java.util.Date
import org.joda.time.Duration;
import org.joda.time.Interval;
// Use .getTime() unless it is a joda DateTime object
Interval interval = new Interval(startDate.getTime(), endDate.getTime());
Duration period = interval.toDuration();
//gives the number of days elapsed between start and end date.
period.getStandardDays();
Similar to days, you can also get hours, minutes and seconds
period.getStandardHours();
period.getStandardMinutes();
period.getStandardSeconds();

Check example here http://www.roseindia.net/java/beginners/DateDifferent.shtml
This example give you difference in days, hours, minutes, secs and milli sec's :).
import java.util.Calendar;
import java.util.Date;
public class DateDifferent {
public static void main(String[] args) {
Date date1 = new Date(2009, 01, 10);
Date date2 = new Date(2009, 07, 01);
Calendar calendar1 = Calendar.getInstance();
Calendar calendar2 = Calendar.getInstance();
calendar1.setTime(date1);
calendar2.setTime(date2);
long milliseconds1 = calendar1.getTimeInMillis();
long milliseconds2 = calendar2.getTimeInMillis();
long diff = milliseconds2 - milliseconds1;
long diffSeconds = diff / 1000;
long diffMinutes = diff / (60 * 1000);
long diffHours = diff / (60 * 60 * 1000);
long diffDays = diff / (24 * 60 * 60 * 1000);
System.out.println("\nThe Date Different Example");
System.out.println("Time in milliseconds: " + diff + " milliseconds.");
System.out.println("Time in seconds: " + diffSeconds + " seconds.");
System.out.println("Time in minutes: " + diffMinutes + " minutes.");
System.out.println("Time in hours: " + diffHours + " hours.");
System.out.println("Time in days: " + diffDays + " days.");
}
}

Use GMT time zone to get an instance of the Calendar, set the time using the set method of Calendar class. The GMT timezone has 0 offset (not really important) and daylight saving time flag set to false.
final Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
cal.set(Calendar.YEAR, 2011);
cal.set(Calendar.MONTH, 9);
cal.set(Calendar.DAY_OF_MONTH, 29);
cal.set(Calendar.HOUR, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
final Date startDate = cal.getTime();
cal.set(Calendar.YEAR, 2011);
cal.set(Calendar.MONTH, 12);
cal.set(Calendar.DAY_OF_MONTH, 21);
cal.set(Calendar.HOUR, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
final Date endDate = cal.getTime();
System.out.println((endDate.getTime() - startDate.getTime()) % (1000l * 60l * 60l * 24l));

Following code can give you the desired output:
String startDate = "Jan 01 2015";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMM dd yyyy");
LocalDate date = LocalDate.parse(startDate, formatter);
String currentDate = "Feb 11 2015";
LocalDate date1 = LocalDate.parse(currentDate, formatter);
System.out.println(date1.toEpochDay() - date.toEpochDay());

public static String getDifferenceBtwTime(Date dateTime) {
long timeDifferenceMilliseconds = new Date().getTime() - dateTime.getTime();
long diffSeconds = timeDifferenceMilliseconds / 1000;
long diffMinutes = timeDifferenceMilliseconds / (60 * 1000);
long diffHours = timeDifferenceMilliseconds / (60 * 60 * 1000);
long diffDays = timeDifferenceMilliseconds / (60 * 60 * 1000 * 24);
long diffWeeks = timeDifferenceMilliseconds / (60 * 60 * 1000 * 24 * 7);
long diffMonths = (long) (timeDifferenceMilliseconds / (60 * 60 * 1000 * 24 * 30.41666666));
long diffYears = (long)(timeDifferenceMilliseconds / (1000 * 60 * 60 * 24 * 365));
if (diffSeconds < 1) {
return "one sec ago";
} else if (diffMinutes < 1) {
return diffSeconds + " seconds ago";
} else if (diffHours < 1) {
return diffMinutes + " minutes ago";
} else if (diffDays < 1) {
return diffHours + " hours ago";
} else if (diffWeeks < 1) {
return diffDays + " days ago";
} else if (diffMonths < 1) {
return diffWeeks + " weeks ago";
} else if (diffYears < 12) {
return diffMonths + " months ago";
} else {
return diffYears + " years ago";
}
}

Best thing to do is
(Date1-Date2)/86 400 000
That number is the number of milliseconds in a day.
One date-other date gives you difference in milliseconds.
Collect the answer in a double variable.

Here's a correct Java 7 solution in O(1) without any dependencies.
public static int countDaysBetween(Date date1, Date date2) {
Calendar c1 = removeTime(from(date1));
Calendar c2 = removeTime(from(date2));
if (c1.get(YEAR) == c2.get(YEAR)) {
return Math.abs(c1.get(DAY_OF_YEAR) - c2.get(DAY_OF_YEAR)) + 1;
}
// ensure c1 <= c2
if (c1.get(YEAR) > c2.get(YEAR)) {
Calendar c = c1;
c1 = c2;
c2 = c;
}
int y1 = c1.get(YEAR);
int y2 = c2.get(YEAR);
int d1 = c1.get(DAY_OF_YEAR);
int d2 = c2.get(DAY_OF_YEAR);
return d2 + ((y2 - y1) * 365) - d1 + countLeapYearsBetween(y1, y2) + 1;
}
private static int countLeapYearsBetween(int y1, int y2) {
if (y1 < 1 || y2 < 1) {
throw new IllegalArgumentException("Year must be > 0.");
}
// ensure y1 <= y2
if (y1 > y2) {
int i = y1;
y1 = y2;
y2 = i;
}
int diff = 0;
int firstDivisibleBy4 = y1;
if (firstDivisibleBy4 % 4 != 0) {
firstDivisibleBy4 += 4 - (y1 % 4);
}
diff = y2 - firstDivisibleBy4 - 1;
int divisibleBy4 = diff < 0 ? 0 : diff / 4 + 1;
int firstDivisibleBy100 = y1;
if (firstDivisibleBy100 % 100 != 0) {
firstDivisibleBy100 += 100 - (firstDivisibleBy100 % 100);
}
diff = y2 - firstDivisibleBy100 - 1;
int divisibleBy100 = diff < 0 ? 0 : diff / 100 + 1;
int firstDivisibleBy400 = y1;
if (firstDivisibleBy400 % 400 != 0) {
firstDivisibleBy400 += 400 - (y1 % 400);
}
diff = y2 - firstDivisibleBy400 - 1;
int divisibleBy400 = diff < 0 ? 0 : diff / 400 + 1;
return divisibleBy4 - divisibleBy100 + divisibleBy400;
}
public static Calendar from(Date date) {
Calendar c = Calendar.getInstance();
c.setTime(date);
return c;
}
public static Calendar removeTime(Calendar c) {
c.set(HOUR_OF_DAY, 0);
c.set(MINUTE, 0);
c.set(SECOND, 0);
c.set(MILLISECOND, 0);
return c;
}

That's probably the most straightforward way to do it - perhaps it's because I've been coding in Java (with its admittedly clunky date and time libraries) for a while now, but that code looks "simple and nice" to me!
Are you happy with the result being returned in milliseconds, or is part of your question that you would prefer to have it returned in some alternative format?

Not using the standard API, no. You can roll your own doing something like this:
class Duration {
private final TimeUnit unit;
private final long length;
// ...
}
Or you can use Joda:
DateTime a = ..., b = ...;
Duration d = new Duration(a, b);

Just to answer the initial question:
Put the following code in a Function like Long getAge(){}
Date dahora = new Date();
long MillisToYearsByDiv = 1000l *60l * 60l * 24l * 365l;
long javaOffsetInMillis = 1990l * MillisToYearsByDiv;
long realNowInMillis = dahora.getTime() + javaOffsetInMillis;
long realBirthDayInMillis = this.getFechaNac().getTime() + javaOffsetInMillis;
long ageInMillis = realNowInMillis - realBirthDayInMillis;
return ageInMillis / MillisToYearsByDiv;
The most important here is to work with long numbers when multiplying and dividing. And of course, the offset that Java applies in its calculus of Dates.
:)

Since the question is tagged with Scala,
import scala.concurrent.duration._
val diff = (System.currentTimeMillis() - oldDate.getTime).milliseconds
val diffSeconds = diff.toSeconds
val diffMinutes = diff.toMinutes
val diffHours = diff.toHours
val diffDays = diff.toDays

If you want to fix the issue for date ranges that cross daylight savings time boundary (e.g. one date in summer time and the other one in winter time), you can use this to get the difference in days:
public static long calculateDifferenceInDays(Date start, Date end, Locale locale) {
Calendar cal = Calendar.getInstance(locale);
cal.setTime(start);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
long startTime = cal.getTimeInMillis();
cal.setTime(end);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
long endTime = cal.getTimeInMillis();
// calculate the offset if one of the dates is in summer time and the other one in winter time
TimeZone timezone = cal.getTimeZone();
int offsetStart = timezone.getOffset(startTime);
int offsetEnd = timezone.getOffset(endTime);
int offset = offsetEnd - offsetStart;
return TimeUnit.MILLISECONDS.toDays(endTime - startTime + offset);
}

Difference between 2 dates in months and days in Java 7

I want to calculate the difference between 2 dates in months and days, I don't want to consider a month is 30 days and get the time in milliseconds and convert them, and I don't want to use a library such as Joda, and I also found a solution that uses LocalDate, however I am using Java 7.
I looked for answers to my question but could not find any, and I tried many approaches, I tried creating a calendar and passed the time in milliseconds the difference between my 2 dates, but if I tried for example getting the difference between 15/04 and 15/5 I would get 30 days and not 1 month, below is the code
Calendar c = Calendar.getInstance();
c.set(Calendar.YEAR, 2013);
c.set(Calendar.MONTH, Calendar.APRIL);
c.set(Calendar.DAY_OF_MONTH, 15);
Date startDate = c.getTime();
c.set(Calendar.YEAR, 2013);
c.set(Calendar.MONTH, Calendar.MAY);
c.set(Calendar.DAY_OF_MONTH, 15);
Date lastDate = c.getTime();
Calendar diffCal = Calendar.getInstance();
diffCal.setTimeInMillis(lastDate.getTime() - startDate.getTime());
int months = ((diffCal.get(Calendar.YEAR) - 1970) * 12) + diffCal.get(Calendar.MONTH);
int days = diffCal.get(Calendar.DAY_OF_MONTH) - 1;
System.out.println("month(s) = " + months); // month(s) = 0
System.out.println("day(s) = " + days); // day(s) = 30
What can I use to get the difference in months first then in days between 2 dates?
EDIT: I wrote the below code and seems to give me what I want, could this be used
Date startDate = sdf.parse("31/05/2016");
Date endDate = sdf.parse("1/06/2016");
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();
startCalendar.setTime(startDate);
endCalendar.setTime(endDate);
int months = 0, days = 0;
months += ((endCalendar.get(Calendar.YEAR) - startCalendar.get(Calendar.YEAR)) * 12);
int startDays = startCalendar.get(Calendar.DAY_OF_MONTH);
int endDays = endCalendar.get(Calendar.DAY_OF_MONTH);
if(endDays >= startDays) {
months += (endCalendar.get(Calendar.MONTH) - startCalendar.get(Calendar.MONTH));
days += (endDays - startDays);
} else {
months += (endCalendar.get(Calendar.MONTH) - startCalendar.get(Calendar.MONTH) - 1);
days += ((startCalendar.getActualMaximum(Calendar.DAY_OF_MONTH) - startDays) + endDays);
}
System.out.println("Difference");
System.out.println("Month(s): " + months);
System.out.println("Day(s): " + days);

You answered your own question in your research. JDK7 does not support what you want. You have three options:
Write your own (do not do this because you will make many mistakes that have been made before)
Use a library like Joda-Time which has been recommended many times
Upgrade to JDK8 and use java.time.Period

Converting date to this format: "X years, X months, X days..."

I am creating a Calendar instance, and setting the date to July 1, 1997 like so:
int currentYear = Calendar.getInstance().get(Calendar.YEAR);
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.set(1997, 6, 1);
What I want to do, is that without using an external library, get the following output from that date (proper calculating of leap years / seconds would be good, but not required) prior to current date (e.g. November 1, 2015 02:45:30):
18 years, 4 months, 0 days, 2 hours, 45 minutes, 30 seconds
I am not quite sure if this is possible at all. I've tried some weird, not very logical calculations, which needed lots of improvements, but couldn't make it work:
int years = currentYear - calendar.get(Calendar.YEAR);
int months = calendar.get(Calendar.MONTH);
if(currentMonth > months) {
years -= 1;
}
UPDATE - Code until now:
Calendar currentDate = Calendar.getInstance();
currentDate.clear();
Calendar birthDate = Calendar.getInstance();
birthDate.clear();
birthDate.set(this.birthYear, this.birthMonth - 1, this.birthDay);
Calendar date = Calendar.getInstance();
date.clear();
date.setTimeInMillis(birthDate.getTimeInMillis() - currentDate.getTimeInMillis());
System.out.println(Integer.toString(date.get(Calendar.YEAR)));

if you are using java 8 then you have LocalDateTime and PlainTimeStamp classes to use
here you find some answers Java 8: Calculate difference between two LocalDateTime

This might help
Calendar startCalendar = Calendar.getInstance();
startCalendar.clear();
startCalendar.set(1997, 6, 1);
Date start = startCalendar.getTime();
Calendar endCalendar = Calendar.getInstance();
// endCalendar.clear();
// endCalendar.set(2015, 10, 1);
Date end = endCalendar.getTime();
long diff = end.getTime() - start.getTime();
long days = TimeUnit.MILLISECONDS.toDays(diff);
long hours = TimeUnit.MILLISECONDS.toHours(diff) % TimeUnit.DAYS.toHours(1);
long minutes = TimeUnit.MILLISECONDS.toMinutes(diff) % TimeUnit.HOURS.toMinutes(1);
long seconds = TimeUnit.MILLISECONDS.toSeconds(diff) % TimeUnit.MINUTES.toSeconds(1);
System.out.println(days + " " + hours + " " + minutes + " " + seconds);
from the days we can write the logic to find the number of leap years, months using modulo division
Java 8 has a new Date API you can try that too since you're using Java 8

how to calculate the difference between 2 dates in java? [duplicate]

I'm using Java's java.util.Date class in Scala and want to compare a Date object and the current time. I know I can calculate the delta by using getTime():
(new java.util.Date()).getTime() - oldDate.getTime()
However, this just leaves me with a long representing milliseconds. Is there any simpler, nicer way to get a time delta?

Simple diff (without lib)
/**
* Get a diff between two dates
* #param date1 the oldest date
* #param date2 the newest date
* #param timeUnit the unit in which you want the diff
* #return the diff value, in the provided unit
*/
public static long getDateDiff(Date date1, Date date2, TimeUnit timeUnit) {
long diffInMillies = date2.getTime() - date1.getTime();
return timeUnit.convert(diffInMillies,TimeUnit.MILLISECONDS);
}
And then can you call:
getDateDiff(date1,date2,TimeUnit.MINUTES);
to get the diff of the 2 dates in minutes unit.
TimeUnit is java.util.concurrent.TimeUnit, a standard Java enum going from nanos to days.
Human readable diff (without lib)
public static Map<TimeUnit,Long> computeDiff(Date date1, Date date2) {
long diffInMillies = date2.getTime() - date1.getTime();
//create the list
List<TimeUnit> units = new ArrayList<TimeUnit>(EnumSet.allOf(TimeUnit.class));
Collections.reverse(units);
//create the result map of TimeUnit and difference
Map<TimeUnit,Long> result = new LinkedHashMap<TimeUnit,Long>();
long milliesRest = diffInMillies;
for ( TimeUnit unit : units ) {
//calculate difference in millisecond
long diff = unit.convert(milliesRest,TimeUnit.MILLISECONDS);
long diffInMilliesForUnit = unit.toMillis(diff);
milliesRest = milliesRest - diffInMilliesForUnit;
//put the result in the map
result.put(unit,diff);
}
return result;
}
http://ideone.com/5dXeu6
The output is something like Map:{DAYS=1, HOURS=3, MINUTES=46, SECONDS=40, MILLISECONDS=0, MICROSECONDS=0, NANOSECONDS=0}, with the units ordered.
You just have to convert that map to a user-friendly string.
Warning
The above code snippets compute a simple diff between 2 instants. It can cause problems during a daylight saving switch, like explained in this post. This means if you compute the diff between dates with no time you may have a missing day/hour.
In my opinion the date diff is kind of subjective, especially on days. You may:
count the number of 24h elapsed time: day+1 - day = 1 day = 24h
count the number of elapsed time, taking care of daylight savings: day+1 - day = 1 = 24h (but using midnight time and daylight savings it could be 0 day and 23h)
count the number of day switches, which means day+1 1pm - day 11am = 1 day, even if the elapsed time is just 2h (or 1h if there is a daylight saving :p)
My answer is valid if your definition of date diff on days match the 1st case
With JodaTime
If you are using JodaTime you can get the diff for 2 instants (millies backed ReadableInstant) dates with:
Interval interval = new Interval(oldInstant, new Instant());
But you can also get the diff for Local dates/times:
// returns 4 because of the leap year of 366 days
new Period(LocalDate.now(), LocalDate.now().plusDays(365*5), PeriodType.years()).getYears()
// this time it returns 5
new Period(LocalDate.now(), LocalDate.now().plusDays(365*5+1), PeriodType.years()).getYears()
// And you can also use these static methods
Years.yearsBetween(LocalDate.now(), LocalDate.now().plusDays(365*5)).getYears()

The JDK Date API is horribly broken unfortunately. I recommend using Joda Time library.
Joda Time has a concept of time Interval:
Interval interval = new Interval(oldTime, new Instant());
EDIT: By the way, Joda has two concepts: Interval for representing an interval of time between two time instants (represent time between 8am and 10am), and a Duration that represents a length of time without the actual time boundaries (e.g. represent two hours!)
If you only care about time comparisions, most Date implementations (including the JDK one) implements Comparable interface which allows you to use the Comparable.compareTo()

int diffInDays = (int)( (newerDate.getTime() - olderDate.getTime())
/ (1000 * 60 * 60 * 24) )
Note that this works with UTC dates, so the difference may be a day off if you look at local dates. And getting it to work correctly with local dates requires a completely different approach due to daylight savings time.

Using the java.time framework built into Java 8+:
ZonedDateTime now = ZonedDateTime.now();
ZonedDateTime oldDate = now.minusDays(1).minusMinutes(10);
Duration duration = Duration.between(oldDate, now);
System.out.println("ISO-8601: " + duration);
System.out.println("Minutes: " + duration.toMinutes());
Output:
ISO-8601: PT24H10M
Minutes: 1450
For more info, see the Oracle Tutorial and the ISO 8601 standard.

tl;dr
Convert your obsolete java.util.Date objects to their replacement, java.time.Instant. Then calculate the elapsed time as a Duration.
Duration d =
Duration.between( // Calculate the span of time between two moments as a number of hours, minutes, and seconds.
myJavaUtilDate.toInstant() , // Convert legacy class to modern class by calling new method added to the old class.
Instant.now() // Capture the current moment in UTC. About two and a half hours later in this example.
)
;
d.toString(): PT2H34M56S
d.toMinutes(): 154
d.toMinutesPart(): 34
ISO 8601 Format: PnYnMnDTnHnMnS
The sensible standard ISO 8601 defines a concise textual representation of a span of time as a number of years, months, days, hours, etc. The standard calls such such a span a duration. The format is PnYnMnDTnHnMnS where the P means "Period", the T separates the date portion from the time portion, and in between are numbers followed by a letter.
Examples:
P3Y6M4DT12H30M5Sthree years, six months, four days, twelve hours, thirty minutes, and five seconds
PT4H30MFour and a half hours
java.time
The java.time framework built into Java 8 and later supplants the troublesome old java.util.Date/java.util.Calendar classes. The new classes are inspired by the highly successful Joda-Time framework, intended as its successor, similar in concept but re-architected. Defined by JSR 310. Extended by the ThreeTen-Extra project. See the Tutorial.
Moment
The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).
Instant instant = Instant.now() ; // Capture current moment in UTC.
Best to avoid the legacy classes such as Date/Calendar. But if you must inter-operate with old code not yet updated to java.time, convert back and forth. Call new conversion methods added to the old classes. For moving from a java.util.Date to an Instant, call Date::toInstant.
Instant instant = myJavaUtilDate.toInstant() ; // Convert from legacy `java.util.Date` class to modern `java.time.Instant` class.
Span of time
The java.time classes have split this idea of representing a span of time as a number of years, months, days, hours, minutes, seconds into two halves:
Period for years, months, days
Duration for days, hours, minutes, seconds
Here is an example.
ZoneId zoneId = ZoneId.of ( "America/Montreal" );
ZonedDateTime now = ZonedDateTime.now ( zoneId );
ZonedDateTime future = now.plusMinutes ( 63 );
Duration duration = Duration.between ( now , future );
Dump to console.
Both Period and Duration use the ISO 8601 standard for generating a String representation of their value.
System.out.println ( "now: " + now + " to future: " + now + " = " + duration );
now: 2015-11-26T00:46:48.016-05:00[America/Montreal] to future: 2015-11-26T00:46:48.016-05:00[America/Montreal] = PT1H3M
Java 9 adds methods to Duration to get the days part, hours part, minutes part, and seconds part.
You can get the total number of days or hours or minutes or seconds or milliseconds or nanoseconds in the entire Duration.
long totalHours = duration.toHours();
In Java 9 the Duration class gets new methods for returning the various parts of days, hours, minutes, seconds, milliseconds/nanoseconds. Call the to…Part methods: toDaysPart(), toHoursPart(), and so on.
ChronoUnit
If you only care about a simpler larger granularity of time, such as “number of days elapsed”, use the ChronoUnit enum.
long daysElapsed = ChronoUnit.DAYS.between( earlier , later );
Another example.
Instant now = Instant.now();
Instant later = now.plus( Duration.ofHours( 2 ) );
…
long minutesElapsed = ChronoUnit.MINUTES.between( now , later );
120
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8 and SE 9 and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
Joda-Time
UPDATE: The Joda-Time project is now in maintenance mode, with the team advising migration to the java.time classes. I leave this section intact for history.
The Joda-Time library uses ISO 8601 for its defaults. Its Period class parses and generates these PnYnMnDTnHnMnS strings.
DateTime now = DateTime.now(); // Caveat: Ignoring the important issue of time zones.
Period period = new Period( now, now.plusHours( 4 ).plusMinutes( 30));
System.out.println( "period: " + period );
Renders:
period: PT4H30M

You need to define your problem more clearly. You could just take the number of milliseconds between the two Date objects and divide by the number of milliseconds in 24 hours, for example... but:
This won't take time zones into consideration - Date is always in UTC
This won't take daylight saving time into consideration (where there can be days which are only 23 hours long, for example)
Even within UTC, how many days are there in August 16th 11pm to August 18th 2am? It's only 27 hours, so does that mean one day? Or should it be three days because it covers three dates?

Days d = Days.daysBetween(startDate, endDate);
int days = d.getDays();
https://www.joda.org/joda-time/faq.html#datediff

A slightly simpler alternative:
System.currentTimeMillis() - oldDate.getTime()
As for "nicer": well, what exactly do you need? The problem with representing time durations as a number of hours and days etc. is that it may lead to inaccuracies and wrong expectations due to the complexity of dates (e.g. days can have 23 or 25 hours due to daylight savings time).

Using millisecond approach can cause problems in some locales.
Lets take, for example, the difference between the two dates 03/24/2007 and 03/25/2007 should be 1 day;
However, using the millisecond route, you'll get 0 days, if you run this in the UK!
/** Manual Method - YIELDS INCORRECT RESULTS - DO NOT USE**/
/* This method is used to find the no of days between the given dates */
public long calculateDays(Date dateEarly, Date dateLater) {
return (dateLater.getTime() - dateEarly.getTime()) / (24 * 60 * 60 * 1000);
}
Better way to implement this is to use java.util.Calendar
/** Using Calendar - THE CORRECT WAY**/
public static long daysBetween(Calendar startDate, Calendar endDate) {
Calendar date = (Calendar) startDate.clone();
long daysBetween = 0;
while (date.before(endDate)) {
date.add(Calendar.DAY_OF_MONTH, 1);
daysBetween++;
}
return daysBetween;
}

Since all the answers here are correct but use legacy java or 3rd party libs like joda or similar, I will just drop another way using new java.time classes in Java 8 and later. See Oracle Tutorial.
Use LocalDate and ChronoUnit:
LocalDate d1 = LocalDate.of(2017, 5, 1);
LocalDate d2 = LocalDate.of(2017, 5, 18);
long days = ChronoUnit.DAYS.between(d1, d2);
System.out.println( days );

There are many ways you can find the difference between dates & times. One of the simplest ways that I know of would be:
Calendar calendar1 = Calendar.getInstance();
Calendar calendar2 = Calendar.getInstance();
calendar1.set(2012, 04, 02);
calendar2.set(2012, 04, 04);
long milsecs1= calendar1.getTimeInMillis();
long milsecs2 = calendar2.getTimeInMillis();
long diff = milsecs2 - milsecs1;
long dsecs = diff / 1000;
long dminutes = diff / (60 * 1000);
long dhours = diff / (60 * 60 * 1000);
long ddays = diff / (24 * 60 * 60 * 1000);
System.out.println("Your Day Difference="+ddays);
The print statement is just an example - you can format it, the way you like.

If you don't want to use JodaTime or similar, the best solution is probably this:
final static long MILLIS_PER_DAY = 24 * 3600 * 1000;
long msDiff= date1.getTime() - date2.getTime();
long daysDiff = Math.round(msDiff / ((double)MILLIS_PER_DAY));
The number of ms per day is not always the same (because of daylight saving time and leap seconds), but it's very close, and at least deviations due to daylight saving time cancel out over longer periods. Therefore dividing and then rounding will give a correct result (at least as long as the local calendar used does not contain weird time jumps other than DST and leap seconds).
Note that this still assumes that date1 and date2 are set to the same time of day. For different times of day, you'd first have to define what "date difference" means, as pointed out by Jon Skeet.

Subtracting the dates in milliseconds works (as described in another post), but you have to use HOUR_OF_DAY and not HOUR when clearing the time parts of your dates:
public static final long MSPERDAY = 60 * 60 * 24 * 1000;
...
final Calendar dateStartCal = Calendar.getInstance();
dateStartCal.setTime(dateStart);
dateStartCal.set(Calendar.HOUR_OF_DAY, 0); // Crucial.
dateStartCal.set(Calendar.MINUTE, 0);
dateStartCal.set(Calendar.SECOND, 0);
dateStartCal.set(Calendar.MILLISECOND, 0);
final Calendar dateEndCal = Calendar.getInstance();
dateEndCal.setTime(dateEnd);
dateEndCal.set(Calendar.HOUR_OF_DAY, 0); // Crucial.
dateEndCal.set(Calendar.MINUTE, 0);
dateEndCal.set(Calendar.SECOND, 0);
dateEndCal.set(Calendar.MILLISECOND, 0);
final long dateDifferenceInDays = ( dateStartCal.getTimeInMillis()
- dateEndCal.getTimeInMillis()
) / MSPERDAY;
if (dateDifferenceInDays > 15) {
// Do something if difference > 15 days
}

Take a look at Joda Time, which is an improved Date/Time API for Java and should work fine with Scala.

int daysDiff = (date1.getTime() - date2.getTime()) / MILLIS_PER_DAY;

Let me show difference between Joda Interval and Days:
DateTime start = new DateTime(2012, 2, 6, 10, 44, 51, 0);
DateTime end = new DateTime(2012, 2, 6, 11, 39, 47, 1);
Interval interval = new Interval(start, end);
Period period = interval.toPeriod();
System.out.println(period.getYears() + " years, " + period.getMonths() + " months, " + period.getWeeks() + " weeks, " + period.getDays() + " days");
System.out.println(period.getHours() + " hours, " + period.getMinutes() + " minutes, " + period.getSeconds() + " seconds ");
//Result is:
//0 years, 0 months, *1 weeks, 1 days*
//0 hours, 54 minutes, 56 seconds
//Period can set PeriodType,such as PeriodType.yearMonthDay(),PeriodType.yearDayTime()...
Period p = new Period(start, end, PeriodType.yearMonthDayTime());
System.out.println(p.getYears() + " years, " + p.getMonths() + " months, " + p.getWeeks() + " weeks, " + p.getDays() + "days");
System.out.println(p.getHours() + " hours, " + p.getMinutes() + " minutes, " + p.getSeconds() + " seconds ");
//Result is:
//0 years, 0 months, *0 weeks, 8 days*
//0 hours, 54 minutes, 56 seconds

If you need a formatted return String like
"2 Days 03h 42m 07s", try this:
public String fill2(int value)
{
String ret = String.valueOf(value);
if (ret.length() < 2)
ret = "0" + ret;
return ret;
}
public String get_duration(Date date1, Date date2)
{
TimeUnit timeUnit = TimeUnit.SECONDS;
long diffInMilli = date2.getTime() - date1.getTime();
long s = timeUnit.convert(diffInMilli, TimeUnit.MILLISECONDS);
long days = s / (24 * 60 * 60);
long rest = s - (days * 24 * 60 * 60);
long hrs = rest / (60 * 60);
long rest1 = rest - (hrs * 60 * 60);
long min = rest1 / 60;
long sec = s % 60;
String dates = "";
if (days > 0) dates = days + " Days ";
dates += fill2((int) hrs) + "h ";
dates += fill2((int) min) + "m ";
dates += fill2((int) sec) + "s ";
return dates;
}

After wading through all the other answers, to keep the Java 7 Date type but be more precise/standard with the Java 8 diff approach,
public static long daysBetweenDates(Date d1, Date d2) {
Instant instant1 = d1.toInstant();
Instant instant2 = d2.toInstant();
long diff = ChronoUnit.DAYS.between(instant1, instant2);
return diff;
}

Note: startDate and endDates are -> java.util.Date
import org.joda.time.Duration;
import org.joda.time.Interval;
// Use .getTime() unless it is a joda DateTime object
Interval interval = new Interval(startDate.getTime(), endDate.getTime());
Duration period = interval.toDuration();
//gives the number of days elapsed between start and end date.
period.getStandardDays();
Similar to days, you can also get hours, minutes and seconds
period.getStandardHours();
period.getStandardMinutes();
period.getStandardSeconds();

Check example here http://www.roseindia.net/java/beginners/DateDifferent.shtml
This example give you difference in days, hours, minutes, secs and milli sec's :).
import java.util.Calendar;
import java.util.Date;
public class DateDifferent {
public static void main(String[] args) {
Date date1 = new Date(2009, 01, 10);
Date date2 = new Date(2009, 07, 01);
Calendar calendar1 = Calendar.getInstance();
Calendar calendar2 = Calendar.getInstance();
calendar1.setTime(date1);
calendar2.setTime(date2);
long milliseconds1 = calendar1.getTimeInMillis();
long milliseconds2 = calendar2.getTimeInMillis();
long diff = milliseconds2 - milliseconds1;
long diffSeconds = diff / 1000;
long diffMinutes = diff / (60 * 1000);
long diffHours = diff / (60 * 60 * 1000);
long diffDays = diff / (24 * 60 * 60 * 1000);
System.out.println("\nThe Date Different Example");
System.out.println("Time in milliseconds: " + diff + " milliseconds.");
System.out.println("Time in seconds: " + diffSeconds + " seconds.");
System.out.println("Time in minutes: " + diffMinutes + " minutes.");
System.out.println("Time in hours: " + diffHours + " hours.");
System.out.println("Time in days: " + diffDays + " days.");
}
}

Use GMT time zone to get an instance of the Calendar, set the time using the set method of Calendar class. The GMT timezone has 0 offset (not really important) and daylight saving time flag set to false.
final Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
cal.set(Calendar.YEAR, 2011);
cal.set(Calendar.MONTH, 9);
cal.set(Calendar.DAY_OF_MONTH, 29);
cal.set(Calendar.HOUR, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
final Date startDate = cal.getTime();
cal.set(Calendar.YEAR, 2011);
cal.set(Calendar.MONTH, 12);
cal.set(Calendar.DAY_OF_MONTH, 21);
cal.set(Calendar.HOUR, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
final Date endDate = cal.getTime();
System.out.println((endDate.getTime() - startDate.getTime()) % (1000l * 60l * 60l * 24l));

Following code can give you the desired output:
String startDate = "Jan 01 2015";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMM dd yyyy");
LocalDate date = LocalDate.parse(startDate, formatter);
String currentDate = "Feb 11 2015";
LocalDate date1 = LocalDate.parse(currentDate, formatter);
System.out.println(date1.toEpochDay() - date.toEpochDay());

public static String getDifferenceBtwTime(Date dateTime) {
long timeDifferenceMilliseconds = new Date().getTime() - dateTime.getTime();
long diffSeconds = timeDifferenceMilliseconds / 1000;
long diffMinutes = timeDifferenceMilliseconds / (60 * 1000);
long diffHours = timeDifferenceMilliseconds / (60 * 60 * 1000);
long diffDays = timeDifferenceMilliseconds / (60 * 60 * 1000 * 24);
long diffWeeks = timeDifferenceMilliseconds / (60 * 60 * 1000 * 24 * 7);
long diffMonths = (long) (timeDifferenceMilliseconds / (60 * 60 * 1000 * 24 * 30.41666666));
long diffYears = (long)(timeDifferenceMilliseconds / (1000 * 60 * 60 * 24 * 365));
if (diffSeconds < 1) {
return "one sec ago";
} else if (diffMinutes < 1) {
return diffSeconds + " seconds ago";
} else if (diffHours < 1) {
return diffMinutes + " minutes ago";
} else if (diffDays < 1) {
return diffHours + " hours ago";
} else if (diffWeeks < 1) {
return diffDays + " days ago";
} else if (diffMonths < 1) {
return diffWeeks + " weeks ago";
} else if (diffYears < 12) {
return diffMonths + " months ago";
} else {
return diffYears + " years ago";
}
}

Best thing to do is
(Date1-Date2)/86 400 000
That number is the number of milliseconds in a day.
One date-other date gives you difference in milliseconds.
Collect the answer in a double variable.

Here's a correct Java 7 solution in O(1) without any dependencies.
public static int countDaysBetween(Date date1, Date date2) {
Calendar c1 = removeTime(from(date1));
Calendar c2 = removeTime(from(date2));
if (c1.get(YEAR) == c2.get(YEAR)) {
return Math.abs(c1.get(DAY_OF_YEAR) - c2.get(DAY_OF_YEAR)) + 1;
}
// ensure c1 <= c2
if (c1.get(YEAR) > c2.get(YEAR)) {
Calendar c = c1;
c1 = c2;
c2 = c;
}
int y1 = c1.get(YEAR);
int y2 = c2.get(YEAR);
int d1 = c1.get(DAY_OF_YEAR);
int d2 = c2.get(DAY_OF_YEAR);
return d2 + ((y2 - y1) * 365) - d1 + countLeapYearsBetween(y1, y2) + 1;
}
private static int countLeapYearsBetween(int y1, int y2) {
if (y1 < 1 || y2 < 1) {
throw new IllegalArgumentException("Year must be > 0.");
}
// ensure y1 <= y2
if (y1 > y2) {
int i = y1;
y1 = y2;
y2 = i;
}
int diff = 0;
int firstDivisibleBy4 = y1;
if (firstDivisibleBy4 % 4 != 0) {
firstDivisibleBy4 += 4 - (y1 % 4);
}
diff = y2 - firstDivisibleBy4 - 1;
int divisibleBy4 = diff < 0 ? 0 : diff / 4 + 1;
int firstDivisibleBy100 = y1;
if (firstDivisibleBy100 % 100 != 0) {
firstDivisibleBy100 += 100 - (firstDivisibleBy100 % 100);
}
diff = y2 - firstDivisibleBy100 - 1;
int divisibleBy100 = diff < 0 ? 0 : diff / 100 + 1;
int firstDivisibleBy400 = y1;
if (firstDivisibleBy400 % 400 != 0) {
firstDivisibleBy400 += 400 - (y1 % 400);
}
diff = y2 - firstDivisibleBy400 - 1;
int divisibleBy400 = diff < 0 ? 0 : diff / 400 + 1;
return divisibleBy4 - divisibleBy100 + divisibleBy400;
}
public static Calendar from(Date date) {
Calendar c = Calendar.getInstance();
c.setTime(date);
return c;
}
public static Calendar removeTime(Calendar c) {
c.set(HOUR_OF_DAY, 0);
c.set(MINUTE, 0);
c.set(SECOND, 0);
c.set(MILLISECOND, 0);
return c;
}

That's probably the most straightforward way to do it - perhaps it's because I've been coding in Java (with its admittedly clunky date and time libraries) for a while now, but that code looks "simple and nice" to me!
Are you happy with the result being returned in milliseconds, or is part of your question that you would prefer to have it returned in some alternative format?

Not using the standard API, no. You can roll your own doing something like this:
class Duration {
private final TimeUnit unit;
private final long length;
// ...
}
Or you can use Joda:
DateTime a = ..., b = ...;
Duration d = new Duration(a, b);

Just to answer the initial question:
Put the following code in a Function like Long getAge(){}
Date dahora = new Date();
long MillisToYearsByDiv = 1000l *60l * 60l * 24l * 365l;
long javaOffsetInMillis = 1990l * MillisToYearsByDiv;
long realNowInMillis = dahora.getTime() + javaOffsetInMillis;
long realBirthDayInMillis = this.getFechaNac().getTime() + javaOffsetInMillis;
long ageInMillis = realNowInMillis - realBirthDayInMillis;
return ageInMillis / MillisToYearsByDiv;
The most important here is to work with long numbers when multiplying and dividing. And of course, the offset that Java applies in its calculus of Dates.
:)

Since the question is tagged with Scala,
import scala.concurrent.duration._
val diff = (System.currentTimeMillis() - oldDate.getTime).milliseconds
val diffSeconds = diff.toSeconds
val diffMinutes = diff.toMinutes
val diffHours = diff.toHours
val diffDays = diff.toDays

If you want to fix the issue for date ranges that cross daylight savings time boundary (e.g. one date in summer time and the other one in winter time), you can use this to get the difference in days:
public static long calculateDifferenceInDays(Date start, Date end, Locale locale) {
Calendar cal = Calendar.getInstance(locale);
cal.setTime(start);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
long startTime = cal.getTimeInMillis();
cal.setTime(end);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
long endTime = cal.getTimeInMillis();
// calculate the offset if one of the dates is in summer time and the other one in winter time
TimeZone timezone = cal.getTimeZone();
int offsetStart = timezone.getOffset(startTime);
int offsetEnd = timezone.getOffset(endTime);
int offset = offsetEnd - offsetStart;
return TimeUnit.MILLISECONDS.toDays(endTime - startTime + offset);
}

Android Days between two dates

I want to compare two dates for my Android application, but I got a really weird issue.
For example:
If I set the back in the past date to 127 days ago:
this.dateEvent = System.currentTimeMillis() - (127 * 24 * 3600 * 1000)
And then compare it to the current date (Days between)
Calendar sDate = getDatePart(new Date(this.dateEvent));
Calendar eDate = getDatePart(new Date(System.currentTimeMillis()));
int daysBetween = 0;
while (sDate.before(eDate))
{
sDate.add(Calendar.DAY_OF_MONTH, 1);
daysBetween ++;
}
while (sDate.after(eDate))
{
eDate.add(Calendar.DAY_OF_MONTH, 1);
daysBetween ++;
}
return daysBetween;
It will return 22 which is not at all what was expected.
Did I make something wrong or is that an issue with the Calendar class ?

Here's a two line solution:
long msDiff = Calendar.getInstance().getTimeInMillis() - testCalendar.getTimeInMillis();
long daysDiff = TimeUnit.MILLISECONDS.toDays(msDiff);
In this example it gets the number of days between date "testCalendar" and the current date.

Please refer this code, this may help you.
public String getCountOfDays(String createdDateString, String expireDateString) {
SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy", Locale.getDefault());
Date createdConvertedDate = null, expireCovertedDate = null, todayWithZeroTime = null;
try {
createdConvertedDate = dateFormat.parse(createdDateString);
expireCovertedDate = dateFormat.parse(expireDateString);
Date today = new Date();
todayWithZeroTime = dateFormat.parse(dateFormat.format(today));
} catch (ParseException e) {
e.printStackTrace();
}
int cYear = 0, cMonth = 0, cDay = 0;
if (createdConvertedDate.after(todayWithZeroTime)) {
Calendar cCal = Calendar.getInstance();
cCal.setTime(createdConvertedDate);
cYear = cCal.get(Calendar.YEAR);
cMonth = cCal.get(Calendar.MONTH);
cDay = cCal.get(Calendar.DAY_OF_MONTH);
} else {
Calendar cCal = Calendar.getInstance();
cCal.setTime(todayWithZeroTime);
cYear = cCal.get(Calendar.YEAR);
cMonth = cCal.get(Calendar.MONTH);
cDay = cCal.get(Calendar.DAY_OF_MONTH);
}
/*Calendar todayCal = Calendar.getInstance();
int todayYear = todayCal.get(Calendar.YEAR);
int today = todayCal.get(Calendar.MONTH);
int todayDay = todayCal.get(Calendar.DAY_OF_MONTH);
*/
Calendar eCal = Calendar.getInstance();
eCal.setTime(expireCovertedDate);
int eYear = eCal.get(Calendar.YEAR);
int eMonth = eCal.get(Calendar.MONTH);
int eDay = eCal.get(Calendar.DAY_OF_MONTH);
Calendar date1 = Calendar.getInstance();
Calendar date2 = Calendar.getInstance();
date1.clear();
date1.set(cYear, cMonth, cDay);
date2.clear();
date2.set(eYear, eMonth, eDay);
long diff = date2.getTimeInMillis() - date1.getTimeInMillis();
float dayCount = (float) diff / (24 * 60 * 60 * 1000);
return ("" + (int) dayCount + " Days");
}

I've finally found the easiest way to deal with that. Here is my code:
public int getTimeRemaining()
{
Calendar sDate = toCalendar(this.dateEvent);
Calendar eDate = toCalendar(System.currentTimeMillis());
// Get the represented date in milliseconds
long milis1 = sDate.getTimeInMillis();
long milis2 = eDate.getTimeInMillis();
// Calculate difference in milliseconds
long diff = Math.abs(milis2 - milis1);
return (int)(diff / (24 * 60 * 60 * 1000));
}
private Calendar toCalendar(long timestamp)
{
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(timestamp);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
return calendar;
}
Hope it helps.

You should never use formula such 24 * 60 * 60 * 1000! Why? Because there is day saving time, and not all days have 24 hours, also what about leap year, that has +1 day. That's why there is a calendar class.
If you do not want to put any external library to your project like Jodatime, you could use pure Calendar class with very efficient function:
public static int numDaysBetween(final Calendar c, final long fromTime, final long toTime) {
int result = 0;
if (toTime <= fromTime) return result;
c.setTimeInMillis(toTime);
final int toYear = c.get(Calendar.YEAR);
result += c.get(Calendar.DAY_OF_YEAR);
c.setTimeInMillis(fromTime);
result -= c.get(Calendar.DAY_OF_YEAR);
while (c.get(Calendar.YEAR) < toYear) {
result += c.getActualMaximum(Calendar.DAY_OF_YEAR);
c.add(Calendar.YEAR, 1);
}
return result;
}

public long Daybetween(String date1,String date2,String pattern)
{
SimpleDateFormat sdf = new SimpleDateFormat(pattern,Locale.ENGLISH);
Date Date1 = null,Date2 = null;
try{
Date1 = sdf.parse(date1);
Date2 = sdf.parse(date2);
}catch(Exception e)
{
e.printStackTrace();
}
return (Date2.getTime() - Date1.getTime())/(24*60*60*1000);
}

Date userDob = new SimpleDateFormat("yyyy-MM-dd").parse(dob);
Date today = new Date();
long diff = today.getTime() - userDob.getTime();
int numOfYear = (int) ((diff / (1000 * 60 * 60 * 24))/365);
int numOfDays = (int) (diff / (1000 * 60 * 60 * 24));
int hours = (int) (diff / (1000 * 60 * 60));
int minutes = (int) (diff / (1000 * 60));
int seconds = (int) (diff / (1000));

I had the same need, I finally ended up using Joda Time, it is very convenient and offers lots of additional functions including the one you are looking for.
You can download the files from here.
Once you included the jar file into your project, you can easily do for example the following:
int daysBetween = Days.daysBetween(new DateTime(sDate), new DateTime(eDate)).getDays();

the best way :-
long fromCalender = Calender.getInstance();
fromCalender.set...// set the from dates
long toCalender = Calender.getInstance();
fromCalender.set...// set the to dates
long diffmili = fromCalender - toCalender;
long hours = TimeUnit.MILLISECONDS.toHours(diffmili);
long days = TimeUnit.MILLISECONDS.toDays(diffmili);
long min = TimeUnit.MILLISECONDS.toMinutes(diffmili);
long sec = TimeUnit.MILLISECONDS.toSeconds(diffmili);

Do like this it supports all Api Levels
Calendar cal = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("MMM dd yyyy HH:mm:ss",
Locale.ENGLISH);
try {
String datestart="June 14 2018 16:02:37";
cal.setTime(sdf.parse(datestart));// all done
Calendar cal1=Calendar.getInstance();
String formatted = sdf.format(cal1.getTime());//formatted date as i want
cal1.setTime(sdf.parse(formatted));// all done
long msDiff = cal1.getTimeInMillis() - cal.getTimeInMillis();
long daysDiff = TimeUnit.MILLISECONDS.toDays(msDiff);
Toast.makeText(this, "days="+daysDiff, Toast.LENGTH_SHORT).show();
} catch (ParseException e) {
e.printStackTrace();
}

fun TimeZone.daysBetween(from: Date, to: Date): Int {
val offset = rawOffset + dstSavings
return ((to.time + offset) / 86400000).toInt() - ((from.time + offset) / 86400000).toInt()
}
Have a try:
val f = SimpleDateFormat("yyyy-MM-dd HH:mm:ss").apply {
timeZone = TimeZone.getTimeZone("GMT")
}
val df = f.parse("2019-02-28 22:59:59")
val dt = f.parse("2019-02-28 23:00:00")
TimeZone.getTimeZone("GMT").daysBetween(df, dt) // 0
TimeZone.getTimeZone("GMT+1").daysBetween(df, dt) // 1

java.time and ThreeTenABP
I should like to contribute the modern answer: Use java.time, the modern Java date and time API for your date work. If developing for Android API level 25 or lower, then through the backport for Android, ThreeTenABP (link at the bottom).
LocalDate eDate = LocalDate.now(ZoneId.of("Europe/Paris"));
LocalDate sDate = eDate.minusDays(127);
long daysBetween = ChronoUnit.DAYS.between(sDate, eDate);
System.out.println(daysBetween);
When I ran this code today, the output was the expected:
127
Notice that the code is not only shorter, just one line for finding the difference; it is also clearer and more natural to read. The classes Date and Calendar that you used are poorly designed and long outdated. I recommend you don’t use them.
What went wrong in your code?
You’ve got an int overflow in your conversion of 127 days to milliseconds. In mathematics 127 * 24 * 3600 * 1000 equals 10 972 800 000. Since the numbers you multiply are ints, Java performs the multiplication in int, and the largest number an int can hold is 2 147 483 647, far from enough for your expected result. In this situation it would have been nice if Java would have thrown an exception or in some other way have made us aware of the error. It doesn’t. It tacitly throws away the high order bits, giving us a result of -1 912 101 888. Subtracting this negative number from the current time is equivalent to adding 22 days and a few hours. This explains why you got 22. Funny that 13 answers have been posted and it seems that no one has spotted this …
Even when doing the multiplication using the long type, it still doesn’t calculate 127 days correctly, though. If the 127 days cross a transition to or from summer time (DST), which in France is the case during 254 of the 365 days of a year, the day of the transition is not 24 hours, but either 23 or 25. Which causes an incorrect number of milliseconds.
You should always leave date math to proven library methods. Never hand code it yourself. It’s more complicated than most of us think, so the risk of doing it incorrectly is high.
Question: Doesn’t java.time require Android API level 26?
java.time works nicely on both older and newer Android devices. It just requires at least Java 6.
In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.
Links
Oracle tutorial: Date Time explaining how to use java.time.
Java Specification Request (JSR) 310, where java.time was first described.
ThreeTen Backport project, the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
ThreeTenABP, Android edition of ThreeTen Backport
Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.

The best solution that worked for me is :
private static int findDaysDiff(long unixStartTime,long unixEndTime)
{
Calendar calendar1 = Calendar.getInstance();
calendar1.setTimeInMillis(unixStartTime);
calendar1.set(Calendar.HOUR_OF_DAY, 0);
calendar1.set(Calendar.MINUTE, 0);
calendar1.set(Calendar.SECOND, 0);
calendar1.set(Calendar.MILLISECOND, 0);
Calendar calendar2 = Calendar.getInstance();
calendar2.setTimeInMillis(unixEndTime);
calendar2.set(Calendar.HOUR_OF_DAY, 0);
calendar2.set(Calendar.MINUTE, 0);
calendar2.set(Calendar.SECOND, 0);
calendar2.set(Calendar.MILLISECOND, 0);
return (int) ((calendar2.getTimeInMillis()-calendar1.getTimeInMillis())/(24 * 60 * 60 * 1000));
}
Since it first converts Hour , Minute, Second and Millisecond to 0 and now the difference will be only in days.

the answer is not correct in some dates like "2019/02/18" , "2019/02/19" but i edit and resolve bug
this is best method :
public int getCountOfDays(String createdDateString, String expireDateString) {
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date createdConvertedDate = null;
Date expireCovertedDate = null;
try {
createdConvertedDate = dateFormat.parse(createdDateString);
expireCovertedDate = dateFormat.parse(expireDateString);
} catch (ParseException e) {
e.printStackTrace();
}
Calendar start = new GregorianCalendar();
start.setTime(createdConvertedDate);
Calendar end = new GregorianCalendar();
end.setTime(expireCovertedDate);
long diff = end.getTimeInMillis() - start.getTimeInMillis();
float dayCount = (float) diff / (24 * 60 * 60 * 1000);
return (int) (dayCount);
}
Enjoy and if was helpefull +vote to this answer ;)

Kotlin Extension:
fun Date?.getDaysBetween(dest: Date?): Int {
if(this == null || dest == null) return 0
val diff = abs(this.time - dest.time)
val dayCount = diff.toFloat() / (24 * 60 * 60 * 1000)
return dayCount.toInt()
}

I am count the days between last submission date and current date if it is less than zero then student cannot give submission. I am working with kotlin. The below code helps you.
var calendar=Calendar.getInstance().time
var dateFormat= SimpleDateFormat("dd/M/yyyy")
var d2=dateFormat.parse(data.get("date").toString())
var cd=dateFormat.format(calendar)
var d1=dateFormat.parse(cd)
var diff=d2.time-d1.time
var ddd= TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS)

This is the Java 8 java.time version which works perfectly for me. You might want to make sure that startDate and endDate are set to the same time, otherwise days might vary by +-1!
These are the Kotlin versions I just copy/pasted.
private fun getDawnOfDay(instant: Instant): Temporal =
LocalDate.from(instant.atZone(ZoneOffset.UTC)).atStartOfDay()
fun getNumberOfDaysInBetween(startDate: Date, endDate: Date) =
Duration.between(getDawnOfDay(startDate.toInstant()), getDawnOfDay(endDate.toInstant()))
.toDays()

I have just modified a little bit most popular answer.
Here is my solution:
daysBetween() - Return days count between two dates.
public static long daysBetween(Date date1, Date date2) {
long msDiff = resetTimeToDateStart(date1).getTime() - resetTimeToDateStart(date2).getTime();
return TimeUnit.MILLISECONDS.toDays(msDiff);
}
private static Date resetTimeToDateStart(Date dDate){
if (Utils.isNull(dDate)){
return null;
}
Calendar calendar = Calendar.getInstance();
calendar.setTime(dDate);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
return calendar.getTime();
}

int difference in days=(present_year - oldyear) * 365 + (present_month - oldmonth)*30 + (present_date-olddate);

All above answers calculating millis_diff / (24 * 60 * 60 * 1000) is simply wrong if you consider 23:59:59 ~ 00:00:00 as two different days and expect offset day count as 1, instead of 0.
A kotlin version gives you count 1, based on #oleksandr-albul answer above.
fun getDayCountBetween(to: Long, from: Long): Int {
if (to <= from) return 0
val calendar = Calendar.getInstance()
var count = 0
// get day count between 'to' and Jan 1st.
calendar.timeInMillis = to
val year = calendar.get(Calendar.YEAR)
count += calendar.get(Calendar.DAY_OF_YEAR)
// minus day count between 'from' and Jan 1st.
calendar.timeInMillis = from
count -= calendar.get(Calendar.DAY_OF_YEAR)
// plus day count of all the gap years.
while (calendar.get(Calendar.YEAR) < year) {
count += calendar.getActualMaximum(Calendar.DAY_OF_YEAR)
calendar.add(Calendar.YEAR, 1)
}
return count
}