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?

That's because 1568814839 is the time in millis but overall it contains a minute, an hour, a day, a month and a year. — coroutineDispatcher, Sep 18 '19 at 14:15
your 1568814839 is: Wednesday, September 18, 2019 1:53:59 and 839 seconds, so when you `get(Calendar.MILLISECOND)` it will return to you 839 — coroutineDispatcher, Sep 18 '19 at 14:17
But Calendar.YEAR returns me 1970 with that millis. Month is 1 and day is 19(839 since 1970 1 1) — sardorkun, Sep 18 '19 at 14:19
yes because you are not setting the other fields, just the time in millis — coroutineDispatcher, Sep 18 '19 at 14:41

Aleks G · Accepted Answer · 2019-09-19T08:23:16.757

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

score 1 · Answer 2 · edited Sep 20 '19 at 16:28

java.time

The modern code would use java.time, the modern Java date and time API.

Feed your count of whole seconds since 1970-01-01T00:00Z to the Instant class:

    ZonedDateTime zdt = Instant.ofEpochSecond(1_568_814_839L)
                               .atZone(ZoneId.of("Asia/Tashkent"));
    System.out.println(zdt);
    System.out.println("Year: " + zdt.getYear());
    System.out.println("Millisecond of second: "
                        + zdt.get(ChronoField.MILLI_OF_SECOND));

Output is:

2019-09-18T18:53:59+05:00[Asia/Tashkent]
Year: 2019
Millisecond of second: 0

As others have said, your number is seconds since the epoch, not milliseconds.

Question: Can I use java.time on Android?

Yes, java.time works nicely on 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 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.

Calendar.setTimeInMillis error - why is that?

2 Answers2

java.time

Question: Can I use java.time on Android?

Links