Joda time, Period to total millis

Question

I'm trying to get the total amount of Milliseconds (not the millis field) from the Period object instance. I've tried multiple conversions, as I couldn't find any method easily giving it.

Has anyone ever needed that and managed to retrieve it ?

(I need this for my patch, to figure out a negative period; negative millis = negative period.)

score 17 · Accepted Answer · answered Mar 08 '12 at 21:42

17

You can't get the millis directly from a Period, since fields like months and years are variable in terms of milliseconds.

In order to make this work, you need to supply a "baseline" instant from which Period can calculate that actual millisecond duration.

For example, the Period.toDurationFrom and Period.toDurationTo methods take such a baseline instant, and calculate a Duration object, which you can then obtain the millis.

The Javadoc for toDurationFrom says:

Gets the total millisecond duration of this period relative to a start instant. This method adds the period to the specified instant in order to calculate the duration.

An instant must be supplied as the duration of a period varies. For example, a period of 1 month could vary between the equivalent of 28 and 31 days in milliseconds due to different length months. Similarly, a day can vary at Daylight Savings cutover, typically between 23 and 25 hours.

So you need to pick an appropriate baseline instant for your application.

answered Mar 08 '12 at 21:42

skaffman

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got it: DateTime zero = new DateTime(0); long millis = period.toDurationFrom(zero).getMillis(); – dror Mar 08 '12 at 21:43
@DrorWeiss: That will work for relatively small periods only. If you start using periods longer than a month, then that may give you a distorted result. – skaffman Mar 08 '12 at 21:45
i've tested it.. so far looks good. though, i will keep watch. Thanks ! ;) – dror Mar 08 '12 at 21:52
6

`toStandardDuration().toMillis()` is a good approximation if you don't expect any weirdness. – Louis Wasserman Mar 09 '12 at 01:52
@skaffman - do you mean wrap around due to limitation in size of long ? If yes, then should i use BigDecimal instead ? – Jedi Knight Mar 17 '13 at 09:43
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In my version of joda time (2.3) it seems to be: `toStandardDuration().getMillis()` – Wim Deblauwe Mar 11 '14 at 09:31
@WimDeblauwe You could add this as answer. – Knight71 Nov 14 '19 at 10:26
@Knight71 just did now. – Wim Deblauwe Nov 14 '19 at 10:32

score 3 · Answer 2 · answered Oct 03 '14 at 01:19

If you want to get the millis from a specific time it can be done by using the plus() or minus() methods of the DateTime class.

e.g. getting the millis from now

 DateTime start = new DateTime();  //NOW
 DateTime end = start.plus(<your period>);
 long millis = end.getMillis() - start.getMillis();

score 2 · Answer 3 · answered Nov 14 '19 at 10:32

2

Using Joda time 2.3, it is:

toStandardDuration().getMillis()

answered Nov 14 '19 at 10:32

Wim Deblauwe

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Joda time, Period to total millis

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