Date date= (new GregorianCalendar(year, month, day)).getTime();
SimpleDateFormat f = new SimpleDateFormat("EEEE");
String dow=f.format(date);
System.out.print("This date is a "+dow);
I have the user input a month(1-12) a day(1-31) and a year(1600-2400)
It works fine only it displays the wrong day. For example it says that Jan 1st 2014 is a Saturday but it was a Wednesday.
It is probably because I didn't factor in leap years but I don't have a clue to go about doing that. Neither do I know how to tell it how many days in each month. An array?
Hopefully minimal lines as well.
Thanks so much!!! This has been bugging me for an hour +. And something so simple, I should have figured. I must be tired.
Thanks!!!!!!!
Month is Zero based. Try,
Date date= (new GregorianCalendar(year, month-1, day)).getTime();
SimpleDateFormat f = new SimpleDateFormat("EEEE");
String dow=f.format(date);
The answer by Shashank Kadne is correct.
Joda-Time
FYI, this work is simpler and cleaner using the Joda-Time 2.3 library.
Joda-Time uses sensible one-based counting for things such as:
Month-of-YearJanuary = 1, February = 2, and so on.
Day-of-WeekMonday = 1, Sunday = 7. (Standard ISO 8601 week)
Joda-Time DateTime objects know their own time zone, unlike java.util.Date objects.
Joda-Time leverages a specified Locale object to render localized strings.
Example Code
// Specify a time zone rather than rely on default.
DateTimeZone timeZone = DateTimeZone.forID( "Europe/Paris" );
int year = 2014;
int month = 1; // Sensible one-based counting. January = 1, February = 2, …
int dayOfMonth = 2;
DateTime dateTime = new DateTime( year, month, dayOfMonth, 0, 0, 0, timeZone );
// Day-of-week info.
int dayOfWeekNumber = dateTime.getDayOfWeek(); // Standard week (ISO 8601). Monday = 1, Sunday = 7.
DateTime.Property dayOfWeekProperty = dateTime.dayOfWeek();
String dayOfWeekName_Short = dayOfWeekProperty.getAsShortText( Locale.FRANCE );
String dayOfWeekName_Long = dayOfWeekProperty.getAsText( Locale.FRANCE );
Dump to console…
System.out.println( "dateTime: " + dateTime );
System.out.println( "dayOfWeekNumber: " + dayOfWeekNumber );
System.out.println( "dayOfWeekName_Short: " + dayOfWeekName_Short );
System.out.println( "dayOfWeekName_Long: " + dayOfWeekName_Long );
When run…
dateTime: 2014-01-02T00:00:00.000+01:00
dayOfWeekNumber: 4
dayOfWeekName_Short: jeu.
dayOfWeekName_Long: jeudi
Without Time & Time Zone
If you truly want only date without any time or time zone, then write similar code but with the LocalDate class.
In Joda Time, one can easily use the DateTimeZone.isLocalDateTimeGap method to tell if a local date and time is invalid because it falls into the gap created by a spring-forward daylight saving time transition.
DateTimeZone zone = DateTimeZone.forID("America/New_York");
LocalDateTime ldt = new LocalDateTime(2013, 3, 10, 2, 0);
boolean inGap = zone.isLocalDateTimeGap(ldt); // true
But how do you detect the fall-back transition? In other words, if a local date and time could be ambiguous because there is an overlap, how do you detect that? I would expect something like zone.isLocalDateTimeOverlap, but it doesn't exist. If it did, I would use it like so:
DateTimeZone zone = DateTimeZone.forID("America/New_York");
LocalDateTime ldt = new LocalDateTime(2013, 11, 3, 1, 0);
boolean overlaps = zone.isLocalDateTimeOverlap(ldt); // true
The Joda-Time documentation is clear that if there is an overlap during conversions, it will take the earlier possibility unless told otherwise. But it doesn't say how to detect that behavior.
Take advantage of withEarlierOffsetAtOverlap()
public static boolean isInOverlap(LocalDateTime ldt, DateTimeZone dtz) {
DateTime dt1 = ldt.toDateTime(dtz).withEarlierOffsetAtOverlap();
DateTime dt2 = dt1.withLaterOffsetAtOverlap();
return dt1.getMillis() != dt2.getMillis();
}
public static void test() {
// CET DST rolls back at 2011-10-30 2:59:59 (+02) to 2011-10-30 2:00:00 (+01)
final DateTimeZone dtz = DateTimeZone.forID("CET");
LocalDateTime ldt1 = new LocalDateTime(2011,10,30,1,50,0,0); // not in overlap
LocalDateTime ldt2 = new LocalDateTime(2011,10,30,2,50,0,0); // in overlap
System.out.println(ldt1 + " is in overlap? " + isInOverlap(ldt1, dtz));
System.out.println(ldt2 + " is in overlap? " + isInOverlap(ldt2, dtz));
}
I want to ask if someone knows any API or something similar that allows me to manage concrete parts of day (for example working hours)
My problem is that I have to manage times in the next context:
imagine I am working in a company which working hours is "8am-2pm" and "3pm-6pm" and with a daylight saving time from "8am to 2pm". I want to know if a concrete moment of a concrete date is a laboral moment or if it isn't.
For example if I have the mentioned calendar, and I ask the API if the "13th august 2012 at 9pm" is a working moment it has to check it and return a correct answer (false in this case) and if I ask if the "13th august 2012 at 9am" is a working moment it has to return "true"
Other important thing related. I have to calculate intervals between two dates with the mentioned calendar. For example, if i set begin time as "today at 5pm" and end time "tomorrow at 10am" it has to return 3 hours (or its equivalent in seconds or milliseconds) because it is the correct time period passed between the begin date and the end date in this calendar.
It also has to work with holidays (particular of each country). I found an API call "JollyTime" but, although it works with holidays, it does not support the working hours...
Any idea?
Update: The Joda-Time library is now in maintenance-mode, its principal author Stephen Colebourne having gone on to lead JSR 310 that defines the java.time classes built into Java 8 and later.
A good database with sophisticated support for date-times may be of assistance here. One such database is Postgres, with good date-time data types and commands ("functions").
The Joda-Time framework may help as well. The Interval class and its parent classes define a span of time between a pair of start & stop date-times. They offer methods for comparison such as: contains, overlaps, isBefore, is After.
Here's some example code to get you started, using Joda-Time 2.3 with Java 7.
// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.
// import org.joda.time.*;
// import org.joda.time.format.*;
DateTimeZone timeZone = DateTimeZone.forID( "Europe/Paris" );
List<Interval> workIntervalsFor13Aug2012 = new ArrayList<Interval>( 2 );
DateTime start, stop;
Interval interval;
start = new DateTime( 2012, 8, 13, 8, 0, 0, timeZone );
stop = new DateTime( 2012, 8, 13, 14, 0, 0, timeZone );
interval = new org.joda.time.Interval( start, stop );
workIntervalsFor13Aug2012.add( interval );
start = new DateTime( 2012, 8, 13, 15, 0, 0, timeZone );
stop = new DateTime( 2012, 8, 13, 18, 0, 0, timeZone );
interval = new org.joda.time.Interval( start, stop );
workIntervalsFor13Aug2012.add( interval );
// Check a date-time against those work intervals.
DateTime test09 = new DateTime( 2012, 8, 13, 9, 0, 0, timeZone );
DateTime test21 = new DateTime( 2012, 8, 13, 21, 0, 0, timeZone );
// You should write a "dateTimeIsInWorkingInterval" method that performs this loop.
Boolean hit = false;
for ( Interval nthInterval : workIntervalsFor13Aug2012 ) {
if( nthInterval.contains( test09 )) {
hit = true;
break;
}
}
if( hit ) {
System.out.println( "This date-time: " + test09 + " occurs during a work interval.");
} else {
System.out.println( "This date-time: " + test09 + " occurs outside a work interval.");
}
hit = false;
for ( Interval nthInterval : workIntervalsFor13Aug2012 ) {
if( nthInterval.contains( test21 )) {
hit = true;
break;
}
}
if( hit ) {
System.out.println( "This date-time: " + test21 + " occurs during a work interval.");
} else {
System.out.println( "This date-time: " + test21 + " occurs outside a work interval.");
}
When run…
This date-time: 2012-08-13T09:00:00.000+02:00 occurs during a work interval.
This date-time: 2012-08-13T21:00:00.000+02:00 occurs outside a work interval.
Take a look at the JODA Time library. I know it has intervals and might be just what you need.
I have implemented a simple solution to calculate working hours between two dates. Starting from this point of view may help you achieve your task.
Here is the class that calculates working time as minutes or miliseconds.
public class WorkingTime {
private static final long ONE_SECOND_AS_MILISECONDS = TimeUnit.SECONDS.convert(1, TimeUnit.SECONDS);
private Integer startHour;
private Integer endHour;
private Integer startMinute;
private Integer endMinute;
public WorkingTime(int startHour, int endHour) {
this(startHour, 0, endHour, 0);
}
public WorkingTime(Integer startHour, Integer startMinute,
Integer endHour, Integer endMinute) {
super();
this.startHour = startHour;
this.endHour = endHour;
this.startMinute = startMinute;
this.endMinute = endMinute;
}
... getters and setters
public long calculateWorkingAsMilis(Date date1, Date date2) {
return ONE_SECOND_AS_MILISECONDS * calculateWorkingSeconds(date1, date2);
}
public long calculateWorkingSeconds(Date date1, Date date2) {
Calendar cal1 = Calendar.getInstance();
cal1.setTime(date1);
setWorkingCalendar(cal1);
Calendar cal2 = Calendar.getInstance();
cal2.setTime(date2);
setWorkingCalendar(cal2);
long day1 = TimeUnit.MILLISECONDS.toDays(cal1.getTimeInMillis());
long day2 = TimeUnit.MILLISECONDS.toDays(cal2.getTimeInMillis());
long daydiff = day2 - day1;
long weekendDiff = (daydiff / 7); // get number of weekends
if (isLeakWeekend(cal1, cal2))
weekendDiff++;
long dailyWorkingTimeAsMinutes = getDailyWorkingTimeAsMinutes();
long secondsToBeDecrementedAsNonWorkingHours = TimeUnit.SECONDS.convert((24 * 60 - dailyWorkingTimeAsMinutes), TimeUnit.MINUTES); // seconds that are not in interval of working hours
long secondsToBeDecrementedAsWorkingHoursForWeekends = TimeUnit.SECONDS.convert(dailyWorkingTimeAsMinutes * 2, TimeUnit.MINUTES); // weekend is not working days, they need to be decremented
long dayDiffAsSeconds = daydiff * secondsToBeDecrementedAsNonWorkingHours;
dayDiffAsSeconds += (weekendDiff * secondsToBeDecrementedAsWorkingHoursForWeekends);
long workDiffSeconds = TimeUnit.SECONDS.convert(
cal2.getTimeInMillis() - cal1.getTimeInMillis(),
TimeUnit.MILLISECONDS) - dayDiffAsSeconds;
return workDiffSeconds;
}
private boolean isLeakWeekend(Calendar cal1, Calendar cal2) {
if (cal1.get(Calendar.DAY_OF_WEEK) > cal2.get(Calendar.DAY_OF_WEEK))
return true;
return false;
}
private long getDailyWorkingTimeAsMinutes() {
return (getEndHour() * 60 + getEndMinute()) - (getStartHour() * 60 + getStartMinute());
}
private Calendar setWorkingCalendar(Calendar cal) {
if (cal.get(Calendar.DAY_OF_WEEK) == Calendar.SUNDAY) {
cal.set(Calendar.DAY_OF_YEAR, cal.get(Calendar.DAY_OF_YEAR) + 1);
resetWorkingHourAndSeconds(cal);
} else if (cal.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) {
cal.set(Calendar.DAY_OF_YEAR, cal.get(Calendar.DAY_OF_YEAR) + 2);
resetWorkingHourAndSeconds(cal);
} else if (cal.get(Calendar.HOUR_OF_DAY) > endHour || (cal.get(Calendar.HOUR_OF_DAY) == endHour && cal.get(Calendar.MINUTE) > endMinute)) {
cal.set(Calendar.HOUR_OF_DAY, endHour);
cal.set(Calendar.MINUTE, endMinute);
} else if (cal.get(Calendar.HOUR_OF_DAY) < startHour || (cal.get(Calendar.HOUR_OF_DAY) == startHour && cal.get(Calendar.MINUTE) < startMinute)) {
cal.set(Calendar.HOUR_OF_DAY, startHour);
cal.set(Calendar.MINUTE, startMinute);
}
return cal;
}
private Calendar resetWorkingHourAndSeconds(Calendar cal) {
cal.set(Calendar.HOUR_OF_DAY, startHour);
cal.set(Calendar.MINUTE, startMinute);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
return cal;
}
}
And here is the usage
// create an instance (working hours from 08:30 to 17:30)
WorkingTime workingTime = new WorkingTime(8, 30, 17, 30);
long durationAsMilis = workingTime.calculateWorkingAsMilis(date1, date2);
Hope that helps
Tuncay Senturk
Im working in a project and I got two types in Date. I want to calculate the number of weeks between these two dates. The dates can be in diffrent years. Is there any good solution for this?
I have tried to implemenent this with Joda-time which was suggested in other topics..
Im not familar with this library, but I tried to do something like this:
public static int getNumberOfWeeks(Date f, Date l){
Calendar c1 = Calendar.getInstance();
Calendar c2 = Calendar.getInstance();
c1.setTime(f);
c2.setTime(l);
DateTime start = new DateTime(c1.YEAR, c1.MONTH, c1.DAY_OF_MONTH, 0, 0, 0, 0);
DateTime end = new DateTime(c2.YEAR, c2.MONTH, c2.DAY_OF_MONTH, 0, 0, 0, 0);
Interval interval = new Interval(start, end);
Period p = interval.toPeriod();
return p.getWeeks();
}
But this is completely wrong... any suggestions ?
Updating answer to account for Java 8
// TechTrip - ASSUMPTION d1 is earlier than d2
// leave that for exercise
public static long getFullWeeks(Calendar d1, Calendar d2){
Instant d1i = Instant.ofEpochMilli(d1.getTimeInMillis());
Instant d2i = Instant.ofEpochMilli(d2.getTimeInMillis());
LocalDateTime startDate = LocalDateTime.ofInstant(d1i, ZoneId.systemDefault());
LocalDateTime endDate = LocalDateTime.ofInstant(d2i, ZoneId.systemDefault());
return ChronoUnit.WEEKS.between(startDate, endDate);
}
It is pretty easy with joda time:
DateTime dateTime1 = new DateTime(date1);
DateTime dateTime2 = new DateTime(date2);
int weeks = Weeks.weeksBetween(dateTime1, dateTime2).getWeeks();
tl;dr
ChronoUnit
.WEEKS
.between(
myJavaUtilDate_Start.toInstant().atZone( ZoneId.of( "Asia/Tokyo" ) ) ,
myJavaUtilDate_Stop.toInstant().atZone( ZoneId.of( "Asia/Tokyo" ) )
)
7
java.time
The java.time framework is built into Java 8 and later. These new classes supplant the old date-time classes bundled with the earliest versions of Java.
The java.time classes also supplant the highly successful Joda-Time framework. Both java.time and Joda-Time are led by Stephen Colbourne.
Instant replaces java.util.Date
The modern class Instant replaces the legacy class java.util.Date. Both represent a moment in UTC, a specific point on the timeline. Both internally use a count since the same epoch reference of the first moment of 1970 in UTC, 1970-01-01T00:00Z. The old class uses a count of milliseconds, while Instant uses a finer count of nanoseconds.
To convert, call new methods added to the old classes.
Instant start = myJavaUtilDateStart.toInstant() ;
Instant stop = myJavaUtilDateStop.toInstant() ;
Let's make this concrete with some example values.
Instant start = OffsetDateTime.of( 2020 , 1 , 23 , 15 , 30 , 0 , 0 , ZoneOffset.UTC ).toInstant();
Instant stop = OffsetDateTime.of( 2020 , 1 , 23 , 15 , 30 , 0 , 0 , ZoneOffset.UTC ).plusWeeks(7 ).toInstant();
Moments versus dates
Both of our Instant objects represent a moment. The goal is a count of weeks. Weeks means days, and days mean certain dates on the calendar.
So we have a bit of a mismatch. For any given moment, the date varies around the globe by time zone. A few minutes after midnight in Paris France is a new date. Meanwhile in Montréal Québec, being several hours behind, that same moment is still “yesterday”, the date before on the calendar. So we cannot directly calculate weeks from a pair of moments.
You must first decide on the time zone by which you want to perceive a calendar for those moments.
Specify a proper time zone name in the format of Continent/Region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime
Apply this ZoneId to our Instant objects to adjust into a time zone, yielding a pair of ZonedDateTime objects.
ZonedDateTime startZdt = start.atZone( z ) ;
ZonedDateTime stopZdt = stop.atZone( z ) ;
ChronoUnit.WEEKS
Now we can use the ChronoUnit enum to calculate elapsed weeks.
long weeks = ChronoUnit.WEEKS.between( startZdt , stopZdt );
Dump to console.
System.out.println( "start.toString() = " + start );
System.out.println( "stop.toString() = " + stop );
System.out.println( "startZdt.toString() = " + startZdt );
System.out.println( "stopZdt.toString() = " + stopZdt );
System.out.println( "weeksCount: " + weeksCount );
See this code run live at IdeOne.com.
start.toString() = 2020-01-23T15:30:00Z
stop.toString() = 2020-03-12T15:30:00Z
startZdt.toString() = 2020-01-23T10:30-05:00[America/Montreal]
stopZdt.toString() = 2020-03-12T11:30-04:00[America/Montreal]
weeksCount: 7
ThreeTen-Extra
The ThreeTen-Extra project adds functionality to the java.time framework built into Java 8 and later.
Weeks class
That project includes a Weeks class to represent a number of weeks. Not only can it calculate, it is also meant to be used in your code as a type-safe object. Such use also helps to make your code self-documenting.
You can instantiate by providing a pair of points in time with the Weeks.between method. Those points in time can be anything implementing java.time.temporal.Temporal including Instant, LocalDate, OffsetDateTime, ZonedDateTime, Year, YearMonth, and more.
Your java.util.Date objects can be easily converted to Instant objects, moments on the timeline in UTC with a resolution in nanoseconds. Look at new methods added to the old date-time classes. For going from Date to Instant, call java.util.Date::toInstant.
Weeks weeks = Weeks.between( startZdt , stopZdt );
You can ask for the number of weeks.
int weeksNumber = weeks.getAmount(); // The number of weeks in this Weeks object.
You can also do much more.
Generate a string in standard ISO 8601 format. The P marks the beginning. The W indicates a number of weeks.
PW7
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.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
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.
Using the date arithmetic in java.util.Calendar:
public static int getWeeksBetween (Date a, Date b) {
if (b.before(a)) {
return -getWeeksBetween(b, a);
}
a = resetTime(a);
b = resetTime(b);
Calendar cal = new GregorianCalendar();
cal.setTime(a);
int weeks = 0;
while (cal.getTime().before(b)) {
// add another week
cal.add(Calendar.WEEK_OF_YEAR, 1);
weeks++;
}
return weeks;
}
public static Date resetTime (Date d) {
Calendar cal = new GregorianCalendar();
cal.setTime(d);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
return cal.getTime();
}
If your requirement is like the start date is 03-Apr-2020 and end date is 07-Apr-2020. the difference between the two dates is 4 days. Now the number of weeks between two dates as 1 for this you can use below snippet.
ChronoUnit.WEEKS.between(LocalDate startDate, LocalDate endDate);
But If your requirement is like 03-Apr-2020 is in one week and 07-Apr-2020 is in another week so you want the number of weeks between two dates as 2 you can use the below snippet.
LocalDate actualStartDate=...
LocalDate actualEndDate=...
LocalDate startDate = actualStartDate.with(TemporalAdjusters.previousOrSame(DayOfWeek.SUNDAY))
LocalDate endDate = actualEndDate.with(TemporalAdjusters.previousOrSame(DayOfWeek.SATURDAY))
long daysBetweenTwoDates = ChronoUnit.DAYS.between(startDate, endDate);
int numberOfWeeks = (int)Math.ceil(daysBetweenTwoDates/7.0);
Tested in java 1.8
Calendar a = new GregorianCalendar(2002,1,22);
Calendar b = new GregorianCalendar(2002,1,28);
System.out.println(a.get(Calendar.WEEK_OF_YEAR));
System.out.println(b.get(Calendar.WEEK_OF_YEAR));
int weeks = b.get(Calendar.WEEK_OF_YEAR)-a.get(Calendar.WEEK_OF_YEAR);
System.out.println(weeks);
try this must work
Calendar calendar1 = Calendar.getInstance();
Calendar calendar2 = Calendar.getInstance();
calendar1.set(2007, 01, 10);
calendar2.set(2007, 07, 01);
long milliseconds1 = calendar1.getTimeInMillis();
long milliseconds2 = calendar2.getTimeInMillis();
long diff = milliseconds2 - milliseconds1;
int diffWeeks = (int)diff / (7*24 * 60 * 60 * 1000);
Here are 2 methods I wrote that not based on an external library.
The first method is when Monday is the first day of the week.
The second method is when Sunday is the first day of the week.
Please read the comments inside the code, there is an option to return the number of the full weeks between 2 dates, and also with the fraction of the remaining days before and after the 2 dates.
public static int getNumberOfFullWeeks(LocalDate startDate,LocalDate endDate)
{
int dayBeforeStartOfWeek = 0;
int daysAfterLastFullWeek = 0;
if(startDate.getDayOfWeek() != DayOfWeek.MONDAY)
{
// get the partial value before loop starting
dayBeforeStartOfWeek = 7-startDate.getDayOfWeek().getValue() + 1;
}
if(endDate.getDayOfWeek() != DayOfWeek.SUNDAY)
{
// get the partial value after loop ending
daysAfterLastFullWeek = endDate.getDayOfWeek().getValue();
}
LocalDate d1 = startDate.plusDays(dayBeforeStartOfWeek); // now it is the first day of week;
LocalDate d2 = endDate.minusDays(daysAfterLastFullWeek); // now it end in the last full week
// Count how many days there are of full weeks that start on Mon and end in Sun
// if the startDate and endDate are less than a full week the while loop
// will not iterate at all because d1 and d2 will be the same date
LocalDate looper = d1;
int counter = 1;
while (looper.isBefore(d2))
{
counter++;
looper = looper.plusDays(1);
}
// Counter / 7 will always be an integer that will represents full week
// because we started to count at Mon and stop counting in Sun
int fullWeeks = counter / 7;
System.out.println("Full weeks between dates: "
+ fullWeeks + " Days before the first monday: "
+ dayBeforeStartOfWeek + " "
+ " Days after the last sunday: " + daysAfterLastFullWeek);
System.out.println(startDate.toString() + " - " + endDate.toString());
// You can also get a decimal value of the full weeks plus the fraction if the days before
// and after the full weeks
float full_weeks_decimal = (float)fullWeeks;
float fraction = ((float)dayBeforeStartOfWeek + (float)daysAfterLastFullWeek) / 7.0F;
System.out.println("Full weeks with fraction: " + String.valueOf(fraction + full_weeks_decimal));
return fullWeeks;
}
public static int getNumberOfFullWeeks_WeekStartAtSunday(LocalDate startDate,LocalDate endDate)
{
int dayBeforeStartOfWeek = 0;
int daysAfterLastFullWeek = 0;
if(startDate.getDayOfWeek() != DayOfWeek.SUNDAY)
{
// get the partial value before loop starting
dayBeforeStartOfWeek = 7-getDayOfWeekBySundayIs0(startDate.getDayOfWeek()) + 1;
}
if(endDate.getDayOfWeek() != DayOfWeek.SATURDAY)
{
// get the partial value after loop ending
daysAfterLastFullWeek = 1+getDayOfWeekBySundayIs0(endDate.getDayOfWeek());
}
LocalDate d1 = startDate.plusDays(dayBeforeStartOfWeek); // now it is the first day of week;
LocalDate d2 = endDate.minusDays(daysAfterLastFullWeek); // now it end in the last full week
// Count how many days there are of full weeks that start on Sun and end in Sat
// if the startDate and endDate are less than a full week the while loop
// will not iterate at all because d1 and d2 will be the same date
LocalDate looper = d1;
int counter = 1;
while (looper.isBefore(d2))
{
counter++;
looper = looper.plusDays(1);
}
// Counter / 7 will always be an integer that will represents full week
// because we started to count at Sun and stop counting in Sat
int fullWeeks = counter / 7;
System.out.println("Full weeks between dates: "
+ fullWeeks + " Days before the first sunday: "
+ dayBeforeStartOfWeek + " "
+ " Days after the last saturday: " + daysAfterLastFullWeek);
System.out.println(startDate.toString() + " - " + endDate.toString());
// You can also get a decimal value of the full weeks plus the fraction if the days before
// and after the full weeks
float full_weeks_decimal = (float)fullWeeks;
float fraction = ((float)dayBeforeStartOfWeek + (float)daysAfterLastFullWeek) / 7.0F;
System.out.println("Full weeks with fraction: " + String.valueOf(fraction + full_weeks_decimal));
return fullWeeks;
}
public static int getDayOfWeekBySundayIs0(DayOfWeek day)
{
if(day == DayOfWeek.SUNDAY)
{
return 0;
}
else
{
// NOTE: getValue() is starting to count from 1 and not from 0
return day.getValue();
}
}
If you want exact number of full weeks use below method, where end date is exclusive:
public static long weeksBetween(Date date1, Date date2) {
return WEEKS.between(date1.toInstant().atZone(ZoneId.systemDefault()).toLocalDate(),
date2.toInstant().atZone(ZoneId.systemDefault()).toLocalDate());
}
If you want a ceil version of this, use below:
public static long weeksBetween(Date date1, Date date2) {
long daysBetween = DAYS.between(date1.toInstant().atZone(ZoneId.systemDefault()).toLocalDate(),
date2.toInstant().atZone(ZoneId.systemDefault()).toLocalDate()) + 1;
return daysBetween / 7 + (daysBetween % 7 == 0 ? 0 : 1);
}
You may do it the following way:
// method header not shown
// example dates:
f = new GregorianCalendar(2009,Calendar.AUGUST,1);
l = new GregorianCalendar(2010,Calendar.SEPTEMBER,1);
DateTime start = new DateTime(f);
DateTime end = new DateTime(l);
// Alternative to above - example dates with joda:
// DateTime start = new DateTime(2009,8,1,0,0,0,0);
// DateTime end = new DateTime(2010,9,1,0,0,0,0);
Interval interval = new Interval(start,end);
int weeksBetween = interval.toPeriod(PeriodType.weeks()).getWeeks();
// return weeksBetween;
This should give you an int representing the number of weeks between the two dates.
Joda Time computes weeks with durations of two dates which may not meet our requirements in some cases. I have a method with Joda Time to compute natural weeks between two dates. Hope it can help you. If you don't use Joda Time, you may modify the code with Calendar to do the same thing.
//Unlike Joda Time Weeks.weeksBetween() that returns whole weeks computed
//from duration, we return natural weeks between two dates based on week of year
public static int weeksBetween(ReadablePartial date1, ReadablePartial date2) {
int comp = date1.compareTo(date2);
if (comp == 0) {
return 0;
}
if (comp > 0) {
ReadablePartial mid = date2;
date2 = date1;
date1 = mid;
}
int year1 = date1.get(DateTimeFieldType.weekyear());
int year2 = date2.get(DateTimeFieldType.weekyear());
if (year1 == year2) {
return date2.get(DateTimeFieldType.weekOfWeekyear()) - date1.get(DateTimeFieldType.weekOfWeekyear());
}
int weeks1 = 0;
LocalDate lastDay1 = new LocalDate(date1.get(DateTimeFieldType.year()), 12, 31);
if (lastDay1.getWeekyear() > year1) {
lastDay1 = lastDay1.minusDays(7);
weeks1++;
}
weeks1 += lastDay1.getWeekOfWeekyear() - date1.get(DateTimeFieldType.weekOfWeekyear());
int midWeeks = 0;
for (int i = year1 + 1; i < year2; i++) {
LocalDate y1 = new LocalDate(i, 1, 1);
int yearY1 = y1.getWeekyear();
if (yearY1 < i) {
y1 = y1.plusDays(7);
midWeeks++;
}
LocalDate y2 = new LocalDate(i, 12, 31);
int yearY2 = y2.getWeekyear();
if (yearY2 > i) {
y2 = y2.minusDays(7);
midWeeks++;
}
midWeeks += y2.getWeekOfWeekyear() - y1.getWeekOfWeekyear();
}
int weeks2 = 0;
LocalDate firstDay2 = new LocalDate(date2.get(DateTimeFieldType.year()), 1, 1);
if (firstDay2.getWeekyear() < firstDay2.getYear()) {
firstDay2 = firstDay2.plusDays(7);
weeks2++;
}
weeks2 += date2.get(DateTimeFieldType.weekOfWeekyear()) - firstDay2.getWeekOfWeekyear();
return weeks1 + midWeeks + weeks2;
}
int startWeek = c1.get(Calendar.WEEK_OF_YEAR);
int endWeek = c2.get(Calendar.WEEK_OF_YEAR);
int diff = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);
int deltaYears = 0;
for(int i = 0;i < diff;i++){
deltaYears += c1.getWeeksInWeekYear();
c1.add(Calendar.YEAR, 1);
}
diff = (endWeek + deltaYears) - startWeek;
Includes the year differences.
This worked for me :)
private int weeksBetween(Calendar startDate, Calendar endDate) {
startDate.set(Calendar.HOUR_OF_DAY, 0);
startDate.set(Calendar.MINUTE, 0);
startDate.set(Calendar.SECOND, 0);
int start = (int)TimeUnit.MILLISECONDS.toDays(
startDate.getTimeInMillis())
- startDate.get(Calendar.DAY_OF_WEEK);
int end = (int)TimeUnit.MILLISECONDS.toDays(
endDate.getTimeInMillis());
return (end - start) / 7;
}
if this method returns 0 they are in the same week
if this method return 1 endDate is the week after startDate
if this method returns -1 endDate is the week before startDate
you get the idea
Without using JodaTime, I was able to accurately calculate the number of weeks between 2 calendars (which accounts for leap years etc.)
private fun calculateNumberOfWeeks() {
val calendarFrom = Calendar.getInstance()
calendarFrom.set(Calendar.HOUR_OF_DAY, 0)
calendarFrom.set(Calendar.MINUTE, 0)
calendarFrom.set(Calendar.SECOND, 0)
calendarFrom.set(Calendar.MILLISECOND, 0)
val calendarTo = Calendar.getInstance()
calendarTo.add(Calendar.MONTH, months)
calendarTo.set(Calendar.HOUR_OF_DAY, 0)
calendarTo.set(Calendar.MINUTE, 0)
calendarTo.set(Calendar.SECOND, 0)
calendarTo.set(Calendar.MILLISECOND, 0)
var weeks = -1
while (calendarFrom.timeInMillis < calendarTo.timeInMillis) {
calendarFrom.add(Calendar.DATE, 7)
weeks++
Log.d(Constants.LOG_TAG, "weeks $weeks")
}
}
Easy way
Calendar cal1 = new GregorianCalendar();
Calendar cal2 = new GregorianCalendar();
cal1.set(2014, 3, 3);
cal2.set(2015, 3, 6);
weekscount.setText("weeks= "+ ( (cal2.getTime().getTime() - cal1.getTime().getTime()) / (1000 * 60 * 60 * 24))/7);
Here is a simple way to find the number of weeks between two dates.
SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
String classStartData = "31 01 2021";
String classEndData = "08 03 2021";
Date dateClassStart = myFormat.parse(classStartData);
Date dateClassEnd = myFormat.parse(classEndData);
long differenceWeek = dateClassEnd.getTime() - dateClassStart.getTime();
int programLength = (int)(TimeUnit.DAYS.convert(differenceWeek, TimeUnit.MILLISECONDS)/7);
System.out.println("Class length in weeks: " +programLength);
After referring many solution, this worked for me.
{Provided I did not want to use external Libraries}
public static int getNumberOfWeeks(Date date1, Date date2) {
if (date1.after(date2)) {
return getNumberOfWeeks(date2, date1);
}
Date date = date1;
int days = 0;
while (date.before(date2)) {
days++;
date = addDays(date, 1);
}
return days/7;
}
To add days to a date :
Date addDays(Date date, int days) {
if (days == 0) {
return date;
} else {
Date shiftedDate = new Date(date.getTime() + (long)days * 86400000L);
return shiftedDate;
}
}
Take a look at the following article: Java - calculate the difference between two dates
The daysBetween method will allow you to get the number of days between dates. Then you can simply divide by 7 to get the number of full weeks.
Calendar date1 = Calendar.getInstance();
Calendar date2 = Calendar.getInstance();
date1.clear();
date1.set(datePicker1.getYear(), datePicker1.getMonth(),
datePicker1.getDayOfMonth());
date2.clear();
date2.set(datePicker2.getYear(), datePicker2.getMonth(),
datePicker2.getDayOfMonth());
long diff = date2.getTimeInMillis() - date1.getTimeInMillis();
float dayCount = (float) diff / (24 * 60 * 60 * 1000);
int week = (dayCount / 7) ;
Hope this might Help you
public int diffInWeeks(Date start, Date end) {
long diffSeconds = (end.getTime() - start.getTime())/1000;
return (int)diffSeconds/(60 * 60 * 24 * 7);
}