Number of days between two dates in Joda-Time

Question

How do I find the difference in Days between two Joda-Time DateTime instances? With ‘difference in days’ I mean if start is on Monday and end is on Tuesday I expect a return

Answer 1

java.time.Period

Use the java.time.Period class to count days.

Since Java 8 calculating the difference is more intuitive using LocalDate, LocalDateTime to represent the two dates

    LocalDate now = LocalDate.now();
    LocalDate inputDate = LocalDate.of(2018, 11, 28);

    Period period = Period.between( inputDate, now);
    int diff = period.getDays();
    System.out.println("diff = " + diff);

Answer 2

Annoyingly, the withTimeAtStartOfDay answer is wrong, but only occasionally. You want:

Days.daysBetween(start.toLocalDate(), end.toLocalDate()).getDays()

It turns out that "midnight/start of day" sometimes means 1am (daylight savings happen this way in some places), which Days.daysBetween doesn't handle properly.

// 5am on the 20th to 1pm on the 21st, October 2013, Brazil
DateTimeZone BRAZIL = DateTimeZone.forID("America/Sao_Paulo");
DateTime start = new DateTime(2013, 10, 20, 5, 0, 0, BRAZIL);
DateTime end = new DateTime(2013, 10, 21, 13, 0, 0, BRAZIL);
System.out.println(daysBetween(start.withTimeAtStartOfDay(),
                               end.withTimeAtStartOfDay()).getDays());
// prints 0
System.out.println(daysBetween(start.toLocalDate(),
                               end.toLocalDate()).getDays());
// prints 1

Going via a LocalDate sidesteps the whole issue.