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, BrazilDateTimeZone 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 0System.out.println(daysBetween(start.toLocalDate(),                               end.toLocalDate()).getDays());// prints 1

Going via a LocalDate sidesteps the whole issue.

Days Class

Using the Days class with the withTimeAtStartOfDay method should work:

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

you can use LocalDate:

Days.daysBetween(new LocalDate(start), new LocalDate(end)).getDays()