Count Down to Christmas with Joda-Time

Question

I am trying to implement Joda-Time to count down to Christmas, but so far I'm struck. I tried java.util.Date and most StackOverflow questions and answers suggested to use Joda-Time. But I can't get it working. Some codes give different answers.

Here are some codes I tried,

DateTime now = new DateTime();
DateTime christmas = new DateTime(2012, 12, 25, 8, 0, 0, 0);
Days daysToChristmas = Days.daysBetween(today, christmas); 
System.out.println(daysToChristmas.toString());

And this prints P187D as answer.

DateTime start = new DateTime(DateTime.now());
DateTime end = new DateTime(2012, 12, 25, 0, 0, 0 ,0);
Interval interval = new Interval(start, end);
Period period = interval.toPeriod();
System.out.println("Seconds " + period.getSeconds());
System.out.println("Minutes " + period.getMinutes());
System.out.println("Hours " + period.getHours());
System.out.println("Days " + period.getDays());

And this prints following result,

Seconds 36
Minutes 21
Hours 7
Days 4

Where I went wrong?

Answer 1

You should be using a Period in order to determine the number of months/days/etc involved:

Period period = new Period(start, end);

Converting an Interval to a period would have been fine too, but parameterless overload includes all period units - and you weren't printing out the months.

Now if you only want days, hours, minutes, seconds then you need to create an appropriate PeriodType, e.g.

PeriodType periodType = PeriodType.dayTime().withMillisRemoved();
Period period = new Period(start, end, periodType);

Then you can ask for those individual fields, and all should be well.

(You could actually use just dayTime(), given that the millis won't interfere with anything else.)

So you can either build your period directly from the start and end as above, or if you want to keep the Interval, you can use:

Period period = interval.toPeriod(periodType);

Answer 2

The first code prints P187D, in ISO 8601 format.

The second code prints only 4 days because you're missing the months (period.getMonths()).