How can I add 1 second in Joda date/time?

I have a LocalDateTime object myDateTime that I can see in the debugger that has:
2015-12-12T23:59:59.000
I do: myDateTime.plusSeconds(1) but the timestamp remains the same.
What am I messing up?

Jon Skeet
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Most types in Joda Time (at least the ones you should use) are immutable. You can't change their value - but you can call methods which return a new value. You're calling the right method in this case, but you need to remember the result, e.g.

myDateTime = myDateTime.plusSeconds(1);

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