I would like to find the "interval" between a datetime A, and another latter one.
You are not looking for an interval (which has anchors on the timeline) but for a duration which is not bound to a specific time on the timeline. Durations based on any time units are called
Period in Joda-Time.
DateTimeFormatter f = DateTimeFormat.forPattern("dd/MM/yyyy HH:mm:ss"); LocalDateTime ldtA = LocalDateTime.parse("21/09/2015 12:00:00", f); LocalDateTime ldtB = LocalDateTime.parse("25/09/2015 12:00:00", f); Period diff = new Period(ldtA, ldtB, PeriodType.dayTime()); System.out.println(PeriodFormat.wordBased(Locale.ENGLISH).print(diff)); // 4 days