Test if Unix time-stamp is today in Java 7

Question

I need to check if a Unix time-stamp (stored as a long) represents today (in my time zone). This is where I am at, but it doesn't seem very elegant:

Calendar tokenTimestamp = Calendar.getInstance();
tokenTimestamp.setTimeInMillis(foo.getDateTimeCreated());

Calendar now = Calendar.getInstance();

if (tokenTimestamp.get(Calendar.DAY_OF_MONTH) != now.get(Calendar.DAY_OF_MONTH)
        || tokenTimestamp.get(Calendar.MONTH) != now.get(Calendar.MONTH)
        || tokenTimestamp.get(Calendar.YEAR) != now.get(Calendar.YEAR)) {
    // Not today...
}

Is there a more correct and/or elegant way to do this?

Answer 1

In Java 7's Calendar, that's probably the best you can do. I'd add just a little detail, specify in what timezone you want the date (as pointed by @Ole V.V.'s comment):

// current date in system default timezone
Calendar.getInstance(TimeZone.getDefault());
// current date in Europe/London timezone
Calendar.getInstance(TimeZone.getTimeZone("Europe/London"));

Also use IANA timezones names (always in the format Continent/City, like America/Sao_Paulo or Europe/Berlin). Avoid using the 3-letter abbreviations (like CST or PST) because they are ambiguous and not standard.

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The old classes (Date, Calendar and SimpleDateFormat) have lots of problems and design issues, and they're being replaced by the new APIs.

For Android you can use the ThreeTen Backport, a great backport for Java 8's new date/time classes, together with the ThreeTenABP (more on how to use it here).

All the classes below are under the org.threeten.bp package. As you're comparing just the date (day/month/year), I'm using the org.threeten.bp.LocalDate class. I also use org.threeten.bp.ZoneId to specify the timezone and the org.threeten.bp.Instant class to convert the long millis value to a date:

// millis value
long millis = 1498499869249L;

// get the date in system default timezone
LocalDate dt = Instant.ofEpochMilli(millis).atZone(ZoneId.systemDefault()).toLocalDate();
// check if it's equals to today
System.out.println(dt.equals(LocalDate.now(ZoneId.systemDefault())));

If you want a different timezone, replace ZoneId.systemDefault() by ZoneId.of("Europe/London") (or whatever timezone name you want - you can get a list of all available timezones by calling ZoneId.getAvailableZoneIds()).

And don't forget to use the same timezone in both lines, to make sure you're comparing the correct values.

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If you want to compare the date and time (day/month/year and hour/minute/second), you can use a org.threeten.bp.LocalDateTime instead:

// get the date in system default timezone
LocalDateTime dt = Instant.ofEpochMilli(millis).atZone(ZoneId.systemDefault()).toLocalDateTime();
// check if it's equals to today
System.out.println(dt.equals(LocalDateTime.now(ZoneId.systemDefault())));