Java last day of month problem

Question

Hello, I'm trying to create a date range to cover a full month, i.e.

[startDate; endDate]

As such, I have a reference date and try to create a new date from it. I'm having problem with the "endDate" because I want it to be near the end of the day (i.e. 23:59:59).

The code I'm using is the following:

  public static Date previousMonthLastDate(Date referenceDate) {
    Calendar calendar = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
    calendar.setTime(referenceDate);
    calendar.add(Calendar.MONTH, -1); // move to the previous month
    int lastDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
    calendar.set(Calendar.DAY_OF_MONTH, lastDay);
    // set the time to be the end of the day
    calendar.set(Calendar.HOUR_OF_DAY, 23);
    calendar.set(Calendar.MINUTE, 59);
    calendar.set(Calendar.SECOND, 59);

    return calendar.getTime();
  }

This code is working as expected on the Android emulator. However, running it on a real phone gives the wrong date. As such, I'm assuming it is some kind of timezone problem.

On the phone, instead of giving say 31/August/2010, it gives 01/September/2010. This value seams to be set after the line of code that sets the HOUR_OF_DAY to 23.

Any ideas?

Thanks.

Answer 1

If you want the timezone to depend on the phone settings, you shouldn't force a timezone when creating your calendar. Just use:

Calendar calendar = Calendar.getInstance();

Answer 2

I can't answer why it's happening, but have you tried setting it to the first day of the next month and subtracting one second/millisecond?

calendar.set(Calendar.DAY_OF_MONTH, 1);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
calendar.add(Calendar.MILLISECOND, -1);