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date.getTime() is shorter than System.getCurrentTimeMillis()

I'm trying to create a simple Alarm Clock, but I stumbled upon a problem that I can't seem to fix. I'm trying to parse a string to a date so I can get the difference between the current time and the time to set off the alarm.
Here's my code to parse the time:
SimpleDateFormat sdf = new SimpleDateFormat("hh:mm:ss");
sdf.setTimeZone(getTimezone());
Date date = sdf.parse(args[0]);
Here's my getTimezone() method:
public static TimeZone getTimezone() {
Calendar cal = Calendar.getInstance();
long milliDiff = cal.get(Calendar.ZONE_OFFSET);
String [] ids = TimeZone.getAvailableIDs();
String name = null;
for (String id : ids) {
TimeZone tz = TimeZone.getTimeZone(id);
if (tz.getRawOffset() == milliDiff) {
// Found a match.
name = id;
break;
}
}
return TimeZone.getTimeZone(name);
}
And here's my code for figuring out the difference:
long diff = date.getTime() - System.currentTimeMillis();
So my problem is that the date.getTime() returns 79680000, while System.currentTimeMillis() returns 1473538047978 (This is of course different every time, but for some odd reason, date.getTime() is not).
Which means that I get a negative number when trying to figure out the difference, and therefore I cannot use it.
EDIT: After a little bit of debugging, I realised that it has to do with the year, month and day not being set, however I do not know how to get those.

You did notice that date.getTime() returns 79680000 which is 22 hours and 20 minutes after 1 January 1970. The problem is (as you noticed) that you did not parse year, month and day.
You can do it by:
SimpleDateFormat sdf = new SimpleDateFormat("DD/MM/YYYY hh:mm:ss");
Example input 20/04/2016 20:20:0 returns time as Mon Jan 04 20:20:00 CET 2016 (don't look at the timezone). It is 1451935200000 miliseconds after 1 January 1970.
Note: change string to match your format requirements (the syntax is self-explanatory).

The accepted answer by Ronin is correct. You are trying to put a time-of-day value into a date-time type.
java.time
Also, you are using troublesome old legacy date-time classes. Now supplanted by the java.time classes.
For a time-of-day value without a date and without a time zone, use LocalTime.
LocalTime alarmTime = LocalTime.parse( "12:34" );
Getting current time-of-day requires a time zone.
ZoneId z = ZoneId.of( "America/Montreal" );
LocalTime now = LocalTime.now( z );
But since we are setting an alarm, we care about the date too.
ZonedDateTime now = ZonedDateTime.now( z );
ZonedDateTime alarm = null;
if ( now.toLocalTime().isBefore( alarmTime ) ) {
alarm = ZonedDateTime.of( now.toLocalDate() , alarmTime , z );
} else {. // Else too late for today, so set alarm for tomorrow.
alarm = ZonedDateTime.of( now.toLocalDate().plusDays( 1 ) , alarmTime , z );
}
To calculate the elapsed time until the alarm, use the Duration class.
Duration untilAlarm = Duration.between( now , alarm );
You can interrogate the duration for a total number of milliseconds. But know that java.time classes are capable of handling nanoseconds.
long millis = untilAlarm.toMillis();

Updated.
You are using only time without a date with you date object in code (parses only time). If you add there date to you time, your date should be comparable to your System.getCurrentTimeMillis() call. And if you subtracting current millis from date in the past, you will have negative numbers. I prefer this convertion (date2 is after date1):
long diffInMillies = date2.getTime() - date1.getTime();
return TimeUnit.convert(diffInMillies, TimeUnit.MILLISECONDS);

Check if time in millis is tomorrow

I want to query SQLite table and get records where the time field (which is a String representing long time in millis) is in the range of tomorrow from querying time.
I also have a field which holds the record date time like this:
dd/MM/yyyy, HH:mm:ss
How would you recommend implementing this?

As per your comment you are open to modify the schema for better performance. So it is better to save time as long (unix timestamp) in database and having an index on that. Once that is done you can simply get tomorrows date at 00:00 in local time zone and convert it to unix timestamp and query based on that. Here is how you can get tomorrows timestamp at 00:00,
public static long getTimeStampAt0000(long timestamp) {
Calendar givenDate = Calendar.getInstance();
givenDate.setTimeInMillis(timestamp);
givenDate.set(Calendar.HOUR_OF_DAY, 0);
givenDate.set(Calendar.MINUTE, 0);
givenDate.set(Calendar.SECOND, 0);
givenDate.set(Calendar.MILLISECOND, 0);
return givenDate.getTimeInMillis();
}
public static long getTimeStampAt0000ForTomorrow() {
long now = System.currentTimeMillis();
long nowAt0000 = getTimeStampAt0000(now);
if (now == nowAt0000) {
// if being queried at 00:00, we are assuming we want same or else we can just remove
// this condition
return nowAt0000;
} else {
return nowAt0000 + 86400000;
}
}

The SQLite doc says that it stores as:
INTEGER as Unix Time, the number of seconds since 1970-01-01 00:00:00 UTC.
Are you certain you have milliseconds since epoch or seconds?
The bundled java.util.Date and Calendar classes are notoriously troublesome. Avoid them. Use either Joda-Time or the new java.time.* package in Java 8.
Note that both java.util.Date and Joda-Time DateTime use milliseconds since epoch, while the new java.time uses nanoseconds. Multiply by 1000L as needed.
When talking about "today" and "tomorrow" with a date-time, you must specify a time zone. The beginning and ending of a day depends on time zone.
// Simulate input.
long millis = DateTime.now().getMillis();
// Use a proper time zone name rather than 3-letter codes.
DateTimeZone timeZone = DateTimeZone.forID( "Asia/Kolkata" ); // Formerly known as Calcutta, India.
DateTime dateTime = new DateTime( millis, timeZone );
DateTime aDayLater = dateTime.plusDays( 1 );
// "Tomorrow" is a span of time.
DateTime startOfToday = new DateTime( timeZone ).withTimeAtStartOfDay();
// Interval comparison is done in "half-open" approach where beginning is inclusive and ending is exclusive.
Interval tomorrow = new Interval( startOfToday.plusDays( 1 ), startOfToday.plusDays( 2 ) );
boolean isDateTimeOccurringTomorrow = tomorrow.contains( dateTime );
boolean isADayLaterOccurringTomorrow = tomorrow.contains( aDayLater );
Dump to console…
System.out.println( "millis: " + millis );
System.out.println( "dateTime: " + dateTime );
System.out.println( "aDayLater: " + aDayLater );
System.out.println( "startOfToday: " + startOfToday );
System.out.println( "tomorrow: " + tomorrow );
System.out.println( "isDateTimeOccurringTomorrow: " + isDateTimeOccurringTomorrow );
System.out.println( "isADayLaterOccurringTomorrow: " + isADayLaterOccurringTomorrow );
When run…
millis: 1392883763016
dateTime: 2014-02-20T13:39:23.016+05:30
aDayLater: 2014-02-21T13:39:23.016+05:30
startOfToday: 2014-02-20T00:00:00.000+05:30
tomorrow: 2014-02-21T00:00:00.000+05:30/2014-02-22T00:00:00.000+05:30
isDateTimeOccurringTomorrow: false
isADayLaterOccurringTomorrow: true

Calculate Date And Time Difference In Java

I have three database (SQLServer) fields:
startDate (Date)
endDate (Date)
Duration (text).
I am calculating date and time difference by using java following code.
public static void main(String[] args) {
DateTimeUtils obj = new DateTimeUtils();
SimpleDateFormat simpleDateFormat =
new SimpleDateFormat("dd/M/yyyy hh:mm:ss");
try {
Date date1 = simpleDateFormat.parse("10/10/2013 11:30:10");
Date date2 = simpleDateFormat.parse("13/10/2013 20:55:55");
obj.printDifference(date1, date2);
} catch (ParseException e) {
e.printStackTrace();
}
}
public void printDifference(Date startDate, Date endDate){
//milliseconds
long different = endDate.getTime() - startDate.getTime();
String diff = "";
System.out.println("startDate : " + startDate);
System.out.println("endDate : "+ endDate);
System.out.println("different : " + different);
diff = String.format("%d:%d", TimeUnit.MILLISECONDS.toHours(different), TimeUnit.MILLISECONDS.toMinutes(different) - TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(different)));
And It returns “HH:MM” and updates the Duration field as String in my database. This works great.
Now there will be multiple duration, what I want to do is once I have Duration, I would like to do add up multiple duration and it should return totalDuration:
For Example:
In my table # 1 I have,
Id | Duration
1001 | 05:04
1001 | 12:19
1001 | 02:16
Table # 2
Id | totalDuration
1001 | 19:39
My Question is: How do I convert HH:Mm to Date and add multiple records together to get totalDuration. Total duration should be text and return the same format “HH:MM

If you actually have date values for start and end in table 1 it would be a lot easier to use datediff and sum the values.

If you still have all the values you worked out then just accumulate a long millisecond count as you go and use that.
If not then there are a few ways, the simplest is probably going to be:
String[] split = duration.split(":");
long duration = Long.parseLong(split[0])*60*60*1000 + Long.parseLong(split[1])*60*1000;
You can then loop through adding up all those durations, then at the end convert it back to a String.
Really you should store the millisecond count in your database and then convert it to text to display though.

Question Not Clear
Your question is not clear. (a) Question fails to address issue of time zones. Are these date-times all in UTC/GMT? (b) Your example dates seem to be 3 days apart, yet your code returns only hours and minutes.
Joda-Time
Trying to roll your own date-time calculations usually leads to trouble and frustration. See if a good date-time library can help you, such as Joda-Time or the new java.time.* classes bundled with Java 8.
ISO 8601 Duration
The international standard for date and time, ISO 8601, defines a way to work with what it calls durations. Historically, the concept has also been called periods. A duration tracks the concept of elapsed time in terms of years, months, days, hours, and minutes.
A value is represented as a string in the format of PnYnMnDTnHnMnS. The 'P' indicates the beginning of a duration (Period) string. A 'T' indicates the time portion. Each number precedes its element designator. For example, "P3Y6M4DT12H30M5S" represents a duration of "three years, six months, four days, twelve hours, thirty minutes, and five seconds".
Joda-Time is ISO 8601 savvy, offering the Period class to represent an ISO duration. A Period can be constructed by passing an ISO duration string. Likewise, the default toString implementation on Period outputs an ISO duration string. You could store that ISO duration string in your database. Joda-Time Period instances can be added together by calling the plus method.
Example Code
Here's example code using Joda-Time 2.3 in Java 7. I sourced the two date-time strings from your question. To demonstrate addition, I add an extra 5 minutes.
Good practice dictates being explicit about time zones rather than rely on defaults. Here I use Paris, choosing so arbitrarily. You may well be using UTC/GMT (no time zone offset), in which case you may pass the pre-defined time zone DateTimeZone.UTC.
// © 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_Paris = DateTimeZone.forID( "Europe/Paris" ); // Or for UTC/GMT, use: DateTimeZone.UTC
DateTimeFormatter formatter = DateTimeFormat.forPattern( "dd/MM/yyyy HH:mm:ss" ).withZone( timeZone_Paris );
DateTime start = formatter.parseDateTime( "10/10/2013 11:30:10" );
DateTime stop = formatter.parseDateTime( "13/10/2013 20:55:55" );
Period period = new Period( start, stop );
DateTime now = new DateTime( timeZone_Paris );
Period period2 = new Period( now , now.plusMinutes( 5 ));
Period total = period.plus( period2 );
Dump to console…
System.out.println( "start: " + start.toString() );
System.out.println( "stop: " + stop.toString() );
System.out.println( "period: " + period.toString() );
System.out.println();
System.out.println( "now: " + now.toString() );
System.out.println( "period2: " + period2.toString() );
System.out.println();
System.out.println( "total: " + total.toString() );
When run…
start: 2013-10-10T11:30:10.000+02:00
stop: 2013-10-13T20:55:55.000+02:00
period: P3DT9H25M45S
now: 2013-12-24T01:03:10.029+01:00
period2: PT5M
total: P3DT9H30M45S
Note how the 25M increased to 30M.
Date-Time Strings
Tip: If you control those date-time strings as shown in your example code, your work will be easier if you switched to using the standard ISO 8601 format. For example: 2013-12-21T21:03:48+05:30 or 2013-12-21T21:03:48Z.
Using the "dd/M/yyyy hh:mm:ss" format is ambiguous. No reason to use that rather than the standard format. A bonus: The standard format gives a chronological order when sorting alphabetically.

check my Calendar date parameter is current date

I just wanted to find date parameter is current date (yyyy-MM-dd) without using simpledateformater or any date to string convertion and then find is equals.
specifiedDate=2012-12-20
currentDate=2012-12-21
specifiedDate == currentDate
to be simple i dont want time (i.e HH:mm:S) not to be included while validating
i have tried something like
public boolean isCurrentDate(Calendar date){
Calendar currentDate = Calendar.getInstance().getTime();
if (currentDate.getDate()==(date.getTime().getDate())
&& currentDate.getMonth()==(date.getTime().getMonth())
&& currentDate.getYear()==(date.getTime().getYear()) )
{
return true;
}
return false;
}
please suggest a better way or if any libraries already available for this !!

What about setting time fields to 0 before comparing
currentDate.set(Calendar.HOUR_OF_DAY, 0);
currentDate.set(Calendar.MINUTE, 0);
currentDate.set(Calendar.SECOND, 0);
currentDate.set(Calendar.MILLISECOND, 0);

Try this if you want to do only
1) Using strings
String s1 = new String("2012-01-27");
String s2 = new String("2011-01-28");
System.out.println(s1.compareTo(s2));
The result will be TRUE if s1 is "bigger" than s2 in lexicographical way and it's what you need. To get more info read javadoc for compareTo() method.
2) Using Joda Time
Using Joda Time lib you can acheive as below
DateTime first = ...;
DateTime second = ...;
LocalDate firstDate = first.toLocalDate();
LocalDate secondDate = second.toLocalDate();
return firstDate.compareTo(secondDate);
I prefer second option

If you are using calendar
public static boolean isSameDay(Calendar cal1, Calendar cal2) {
if (cal1 == null || cal2 == null) {
throw new IllegalArgumentException("The dates must not be null");
}
return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA) &&
cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR) &&
cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR));
}
public static boolean isToday(Calendar cal) {
return isSameDay(cal, Calendar.getInstance());
}
If you are using Date
public static boolean isSameDay(Date date1, Date date2) {
if (date1 == null || date2 == null) {
throw new IllegalArgumentException("The dates must not be null");
}
Calendar cal1 = Calendar.getInstance();
cal1.setTime(date1);
Calendar cal2 = Calendar.getInstance();
cal2.setTime(date2);
return isSameDay(cal1, cal2);
}
public static boolean isToday(Date date) {
return isSameDay(date, Calendar.getInstance().getTime());
}

Your last line && currentDate.getYear()==(date.getMonth()) ) appears to be comparing the year and month not the year and year. Could this be your issue?

Try this:
currentDate.set(Calendar.DATE, 0);

Time Zone
The example code in your question ignores the crucial issue of time zone. The date, that is the beginning and ending points of a day, is defined by a time zone.
Both java.util.Calendar and java.util.Date have no time zone assigned. They represent a date and a time in UTC/GMT.
So you need to apply a desired time zone, relevant to the context of your app & data. That means you need a decent date-time library. Something other than java.util.Date/Calendar, java.text.SimpleDateFormat and their sibling classes, as they are notoriously troublesome. Use either Joda-Time or the new java.time.* package bundled with Java 8 (inspired by Joda-Time, defined by JSR 310).
Note the use of the method withTimeAtStartOfDay. That gets the first moment of the day. That is usually the time 00:00:00 but not always. Daylight Saving Time (DST) or other anomalies may produce a different time. That method smartly handles such issues.
Today = Span of Time
Technically, when working with date-time values, a particular "date" is actually a span of time. The most common and generally useful way to define that span is "half-open" where the beginning is inclusive and the ending is exclusive. That means, for current date, we want the first moment of today (inclusive) to the first moment of tomorrow (exclusive). Then we ask if the target date-time falls within that span.
There are other ways to get this job done. I'm showing this approach because it is applies to situations beyond the question of "today".
Joda-Time
Joda-Time offers three classes for defining a span of time: Interval, Period, and Duration.
Example Code
Setup our input data, a Calendar object.
// Create a Calendar object to simulate input.
java.util.Date date = DateTime.now().minusDays( 3 ).toDate();
java.util.Calendar cal = java.util.Calendar.getInstance();
cal.setTime( date );
Define "today" as a span of time, and see if target date-time falls within that span.
DateTimeZone timeZone = DateTimeZone.forID( "Asia/Kolkata" );
DateTime dateTimeInQuestion = new DateTime( cal.getTimeInMillis(), timeZone );
DateTime now = new DateTime( timeZone );
Interval today = new Interval( now.withTimeAtStartOfDay(), now.plusDays( 1 ).withTimeAtStartOfDay() );
boolean isDateTimeInQuestionInInterval = today.contains( dateTimeInQuestion );
Dump to console…
System.out.println( "cal: " + cal.getTime() );
System.out.println( "dateTimeInQuestion: " + dateTimeInQuestion );
System.out.println( "now: " + now );
System.out.println( "today: " + today );
System.out.println( "isDateTimeInQuestionInInterval: " + isDateTimeInQuestionInInterval );
When run…
cal: Wed Feb 12 22:46:04 PST 2014
dateTimeInQuestion: 2014-02-13T12:16:04.369+05:30
now: 2014-02-16T12:16:04.497+05:30
today: 2014-02-16T00:00:00.000+05:30/2014-02-17T00:00:00.000+05:30
isDateTimeInQuestionInInterval: false

Check if 24 hours have passed (reading from a string)

I am saving date's in a file in the following format as a string.
Sat Jul 21 23:31:55 EDT 2012
How can I check if 24 hours have passed? I am a beginner so please explain it a little bit =)

I am not sure if I completely understood the question - do you have two dates for comparison or do you wish to keep checking periodically if 24 hours have elapsed?
If comparing two date/times, I would suggest looking at joda or perhaps date4j. Using joda, one could look into using interval between two dates:
Interval interval = new Interval(previousTime, new Instant());
where previous time would be the time you mentioned

You can do something like this:
try {
// reading text...
Scanner scan = new Scanner( new FileInputStream( new File( "path to your file here..." ) ) );
String dateString = scan.nextLine();
// creating a formatter.
// to understand the format, take a look here: http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html
// EEE: Day name of week with 3 chars
// MMM: Month name of the year with 3 chars
// dd: day of month with 2 chars
// HH: hour of the day (0 to 23) with 2 chars
// mm: minute of the hour with 2 chars
// ss: second of the minute with 2 chars
// zzz: Timezone with 3 chars
// yyyy: year with 4 chars
DateFormat df = new SimpleDateFormat( "EEE MMM dd HH:mm:ss zzz yyyy", Locale.US );
// parsing the date (using the format above, that matches with your date string)
Date date = df.parse( dateString );
// now!
Date now = new Date();
// gets the differente between the parsed date and the now date in milliseconds
long diffInMilliseconds = now.getTime() - date.getTime();
if ( diffInMilliseconds < 0 ) {
System.out.println( "the date that was read is in the future!" );
} else {
// calculating the difference in hours
// one hour have: 60 minutes or 3600 seconds or 3600000 milliseconds
double diffInHours = diffInMilliseconds / 3600000D;
System.out.printf( "%.2f hours have passed!", diffInHours );
}
} catch ( FileNotFoundException | ParseException exc ) {
exc.printStackTrace();
}

I would suggest storing your information as a java.util.Calendar which has a compareTo ()function.
If you want to compare now to current time, you can use System.getCurrentTimeMillis() to get the current time.

Define A Day
Do you really mean one day or 24-hours? Because of Daylight Saving Time nonsense, a day can vary in length such as 23 or 25 hours in the United States.
Avoid 3-Letter Time Zone Codes
That String format is a terrible representation of a date-time. It is difficult to parse. It uses a 3-letter time zone code, and such codes are neither standardized nor unique. If possible, choose another format. The obvious choice is ISO 8601, for example: 2014-07-08T04:17:01Z.
Use proper time zone names.
Avoid j.u.Date & .Calendar
The java.util.Date and .Calendar classes bundled with Java are notoriously troublesome. Avoid them.
Instead use either the venerable Joda-Time library or the new java.time package bundled in Java 8 (and inspired on Joda-Time).
Joda-Time
Here is some example code in Joda-Time.
Get the current moment.
DateTime now = DateTime.now();
Parse the input string.
String input = "Sat Jul 21 23:31:55 EDT 2012";
DateTime formatter = DateTimeFormat.forPattern( "EEE MMM dd HH:mm:ss zzz yyyy" ).with Locale( java.util.Locale.ENGLISH );
DateTime target = formatter.parseDateTime( input );
Calculate 24 hours (or next day).
DateTime twentyFourHoursLater = target.plusHours( 24 );
Test if current moment happened after.
boolean expired = now.isAfter( twentyFourHoursLater );
Or, if you want next day rather than 24-hours, use plusDays rather than plusHours. If necessary, adjust to desired time zone. Time zone is crucial as it defines the day/date and applies rules for anomalies such as Daylight Saving Time.
DateTime targetAdjusted = target.withZone( DateTimeZone.forID( "Europe/Paris" ) );
…
DateTime aDayLater = targetAdjusted.plusDays( 1 ); // Go to next day, accounting for DST etc.
boolean expired = now.isAfter( aDayLater ); // Test if current moment happened after.