Get Today's date in Java at midnight time

Question

I need to create two date objects. If the current date and time is March 9th 2012 11:30 AM then

• date object d1 should be 9th March 20

Answer 1

Defining ‘Midnight’

The word “midnight” is tricky to define.

Some think of it as the moment before a new day starts. Trying to represent that in software as tricky as the last moment of the day can always be subdivided as a smaller fraction of a second.

I suggest a better way of thinking about this is to get “first moment of the day”.

This supports the commonly used approach of defining a span of time as ‘Half-Open’, where the beginning is inclusive while the ending is exclusive. So a full day starts with the first moment of the day and runs up to, but not including, the first moment of the following day. A full day would like this (notice the date going from the 3rd to the 4th):

2016-02-03T00:00:00.0-08:00[America/Los_Angeles]/2016-02-04T00:00:00.0-08:00[America/Los_Angeles]

Joda-Time

If using the Joda-Time library, call withTimeAtStartOfDay.

Note how we specify the time zone. If omitted, the JVM’s current default time zone is implicitly applied. Better to be explicit.

DateTime todayStart = DateTime.now( DateTimeZone.forID( "America/Montreal" ) ).withTimeAtStartOfDay() ;

If using Java 8 or later, better to use the java.time package built into Java. See sibling Answer by Jens Hoffman.