Java equivalent of .NET DateTime.MinValue, DateTime.Today

Question

Is there a Java equivalent of DateTime.MinValue and DateTime.Today in the Java Date class? Or a way of achieving something similar?

I've realised how spoilt you are with the .NET datetime class, I also need the equivalent of AddDays(), AddMonths().

Answer 1

The de-facto Java datetime API is joda-time.

With it, you can get the current date/time by just constructing new DateTime().

Similarly, Without it, you can use Calendar.getInstance() or new Date() to obtain the current date/time.

MinValue can be Calendar.getInstance(0) / new Date(0). This would use the default chronology - i.e. since January 1st, 1970. Since MinValue returns Januar 1st, year 1, you can do that be simply specifying this date, using the appropriate constructor of DateTime.

Answer 2

The other Answers may be correct but use outmoded classes.

java.time

The old date-time classes (java.util.Date/.Calendar etc.) were supplanted by Joda-Time, which in turn has been supplanted by the java.time framework built into Java 8 and later. The java.time classes are inspired by Joda-Time, defined by JSR 310, extended by the ThreeTen-Extra project, back-ported to Java 6 & 7 by the ThreeTen-Backport project, and adapted to Android in the ThreeTenABP project. See Tutorial.

To get the current moment on the timeline in UTC with a resolution of nanoseconds, use Instant.

Instant now = Instant.now();

Instant has three constants:

• EPOCH – 1970-01-01T00:00:00Z
• MIN – -1000000000-01-01T00:00Z
• MAX – 1000000000-12-31T23:59:59.999999999Z

To get the current moment for an offset-from-UTC, apply a ZoneOffset to get an OffsetDateTime.

OffsetDateTime now = OffsetDateTime.now( ZoneOffset.of( "-04:00" ) );

Better to apply a full time zone (offset plus rules for anomalies such as Daylight Saving Time) if known. Apply a ZoneId to get a ZonedDateTime.

ZonedDateTime now = ZonedDateTime.now( ZoneId.of( "America/Montreal" ) );

You can perform arithmetic.

ZonedDateTime dayLater = now.plusDays( 1 );
ZonedDateTime monthLater = now.plusMonths( 1 );

You can get the first moment of a day.

ZoneId zoneId = ZoneId.of( "America/Montreal" );
ZonedDateTime tomorrowStart = now.toLocalDate().atStartOfDay( zoneId );  // Usually time-of-day of `00:00:00.0` but not always.

If you need only a date without time-of-day and without time zone, use LocalDate. Similarly, LocalTime for time-only without date and without time zone. Usually better to stick with Instant and OffsetDateTime/ZonedDateTime as the Local… types do not represent actual moments on the timeline (no offset or time zone means they are undefined).

LocalDate localDate = LocalDate.now( zoneId );
LocalTime localTime = LocalTime.now( zoneId );