java difference between calendars

Question

I'm just doing a simple difference of two timemilisseconds of two different calendar.

Example:

    Calendar ini = Calendar.getInstance();
    try {
        Thread.sleep(1500);
    } catch (InterruptedException e) {e.printStackTrace();}

    Calendar end = Calendar.getInstance();
    long diff = end.getTimeInMillis()-ini.getTimeInMillis();
    System.out.println("diff "+diff);
    System.out.println("ini date "+ ini.getTime());
    System.out.println("end date "+ end.getTime());
    System.out.println("diff time format "+timeFormat.format(diff));

The time format is:

private final static String TIME_STRING_FORMAT = "hh:mm:ss.SSS";
private static SimpleDateFormat timeFormat = new SimpleDateFormat(TIME_STRING_FORMAT);

And in the output, always appear 1 our of difference, is it problem of the SimpleDateFormat???

Output:

diff 1500
ini date Sun May 24 22:27:01 CEST 2015
end date Sun May 24 22:27:03 CEST 2015
diff time format 01:00:01.500

Thanks for your help!!

I don't know of any overload of `SimpleDateFormat#format` that receives a `long` to parse. Please provide the exact code to replicate your issue. — Luiggi Mendoza, May 24 '15 at 20:40

Kasper van den Berg · Answer 1 · 2015-05-25T08:08:59.727

2

The 1 hour difference is caused by your local time zone. Date(long) constructs a date a number of milli seconds after January 1st 1970 GMT. In continental Europe (during winter) 1500 milli seconds after the epoch is thus January 1st 01:00:01.500.

If you use Java 8 see the tutorial on Period and Duration. Duration is probably what you want to use.

edited May 25 '15 at 08:08

answered May 24 '15 at 20:46

Kasper van den Berg

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Yes. Avoid using java.util.Date/.Calendar and SimpleDateFormat. Use java.time package built into Java 8 and later, or use Joda-Time. – Basil Bourque May 25 '15 at 06:49
Sounds great, but I can't use it in Android :) Any idea? Thanks! – jurmeneta May 30 '15 at 17:44

score 2 · Accepted Answer · edited May 23 '17 at 12:30

It looks like SimpleDateFormat uses a timezone. See this related question. So when you give it the time 1500 milliseconds, it thinks you're giving it the time since the beginning of epoch time in the GMT time. Then it translates this to your timezone, giving you some hours of offset. You probably want to set the timezone on your timeFormat to GMT. Try this:

    Calendar ini = Calendar.getInstance();
    try {
        Thread.sleep(1500);
    } catch (InterruptedException e) {e.printStackTrace();}

    Calendar end = Calendar.getInstance();
    long diff = end.getTimeInMillis()-ini.getTimeInMillis();
    System.out.println("diff "+diff);
    System.out.println("ini date "+ ini.getTime());
    System.out.println("end date "+ end.getTime());
    Date date = new Date(diff);
    System.out.println(date);
    timeFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
    System.out.println("diff time format "+timeFormat.format(date));

Changing the timezone in the SimpleDateFormat works. +1 For explaining where the error was coming from. — goncalotomas, May 24 '15 at 21:08

java difference between calendars

2 Answers2