Add one day into Joda-Time DateTime

Question

I have date Wed May 08 00:00:00 GMT+06:30 2013. I add one day into it by using Joda-Time DateTime like this.

DateTime dateTime = new DateTime(date);
dateTime.plusDays(1);

When I print dateTime, I got this date 2013-05-08T00:00:00.000+06:30. The joda date time didn't add one day. I haven't found any error.

Thanks

I don't know joda, but I assume `plusDays()` returns a new `DateTime` object. Try `datetime = dateTime.plusDays(1)`. Confirmed from the [docs](http://joda-time.sourceforge.net/apidocs/org/joda/time/DateTime.html#plusDays%28int%29). — Phylogenesis, May 09 '13 at 12:07
@Phylogenesis you might want to post that as an answer, because it is correct. — Barend, May 09 '13 at 12:08
@Barend it's been posted as an answer now. No need to clutter the question. — Phylogenesis, May 09 '13 at 12:10
I was apparently in the process of posting the answer when the comment thread happened. Had I seen it happening, I would have agreed Phylogenesis should post as an answer. — Don Roby, May 09 '13 at 12:39

score 178 · Accepted Answer · answered May 09 '13 at 12:08

178

The plusDays method is not a mutator. It returns a copy of the given DateTime object with the change made rather than changing the given object.

If you want to actually change the variable dateTime value, you'll need:

DateTime dateTime = new DateTime(date);
dateTime = dateTime.plusDays(1);

answered May 09 '13 at 12:08

Don Roby

maybe add the words 'Immutable' and 'Mutable' to best explain this to such a question – Samuel Owino Dec 02 '20 at 17:36

score 32 · Answer 2 · edited Jan 08 '20 at 13:38

32

If you want add days to current date time instance, use MutableDateTime

MutableDateTime dateTime = new MutableDateTime(date);  
dateTime.addDays(1);

edited Jan 08 '20 at 13:38

JodaStephen

answered May 10 '13 at 06:49

Ilya

2 Answers2