Calendar.setTimeInMillis error - why is that?

Question

calendar gets wrong unix time as I got.

long millis = 1568814839L;
System.out.println(millis); //1568814839
Calendar.getInstance(TimeZone.getTimeZone("Asia/Tashkent"));
calendar.setTimeInMillis(millis);
System.out.println(calendar.get(Calendar.MILLISECOND));//839

What should I do? Calendar.YEAR should be 2019 with that millis. However, calendar gives me 1970, why?

Answer 1

The error is due to you confusing time in milliseconds and time in seconds. 1568814839L is the number of seconds since 1/1/1970, but you're treating it as milliseconds. This is quite easy to check:

long millis = 1568814839L;
System.out.println(millis); //1568814839
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("Asia/Tashkent"));
System.out.println(calendar.getTimeInMillis()); //1568820981321
calendar.setTimeInMillis(millis);
System.out.println(calendar.get(Calendar.YEAR));//839

This will produce:

1568814839
1568820981321
1970

As you can see, your number is 3 orders of magnitude off. Add three 0's to the end of your millis number:

long millis = 1568814839000L;
...
System.out.println(calendar.get(Calendar.YEAR));

Now you get:

1568814839000
1568821211006
2019