How to get the the number of days between two dates - `java.util.Calendar`

I'm trying to get the number of days between two dates. I'm working from Agenda, JFXtras.

The start time = getStartTime() returns java.util.Calendar
The end time = getEndTime() returns java.util.Calendar

This is what I've got so far:

void printAppointment(Appointment a) throws ParseException {
        System.out.println(a.getSummary());
        System.out.println(a.getDescription());

        DateFormat formatter = new SimpleDateFormat("yyyy, MMM dd h:mm:ss a z");
        System.out.println(formatter.format(a.getStartTime().getTime()));
        System.out.println(formatter.format(a.getEndTime().getTime()));
        System.out.println(a.getAppointmentGroup());
        System.out.println(a.getLocation());

        // My problem starts here
        Calendar cal1 = new GregorianCalendar();
        Calendar cal2 = new GregorianCalendar();

        SimpleDateFormat sdf = new SimpleDateFormat("ddMMyyyy");

        Date date = sdf.parse(formatter.format(a.getStartTime().getTime()));
        cal1.setTime(date);
        date = sdf.parse(formatter.format(a.getEndTime().getTime()));
        cal2.setTime(date);
        // System.out.println("Days difference = " + daysBetween(cal1.getTime(), cal2.getTime()));
        System.out.println("Days difference = can't be set");
    }

    private int daysBetween(Date d1, Date d2) {
        return (int) ((d2.getTime() - d1.getTime()) / (1000 * 60 * 60 * 24));
    }

After // My problem starts here I get nothing. The following gets printed:

Another Morning appointment
Another Description of morning appointment
2014, Jun 12 6:00:00 AM PDT
2014, Jun 13 2:00:00 AM PDT
jfxtras.labs.scene.control.Agenda$AppointmentGroupImpl@16e4577
null

Note that the difference in days gets left out.

If anyone could help me out, I'll be more than greatful. Thank you all.

Update:

This is the final working implementation that does the difference in Days, Hours, Minutes and seconds as the attempt below shows.

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2014. Jun Mon.9 3:18PM
2014. Jun Wed.11 3:18PM
jfxtras.labs.scene.control.Agenda$AppointmentGroupImpl@12e3872
null
diffSeconds difference = 172800
diffMinutes difference = 2880
diffHours difference = 48
diffDays difference = 2

This is the code that does that

void printAppointment(Appointment a) {
    System.out.println(a.getSummary());
    System.out.println(a.getDescription());

    DateFormat formatter = new SimpleDateFormat("yyyy. MMM EEE.d h:mma");
    System.out.println(formatter.format(a.getStartTime().getTime()));
    System.out.println(formatter.format(a.getEndTime().getTime()));
    System.out.println(a.getAppointmentGroup());
    System.out.println(a.getLocation());
    this.daysBetween(a.getStartTime().getTimeInMillis(), a.getEndTime().getTimeInMillis());

}

private void daysBetween(long t1, long t2) {
    int diff = (int) (t2 - t1);

    long diffSeconds = diff / 1000;
    long diffMinutes = diff / (60 * 1000);
    long diffHours = diff / (60 * 60 * 1000);
    long diffDays = diff / (24 * 60 * 60 * 1000);

    System.out.println("diffSeconds difference = " + diffSeconds);
    System.out.println("diffMinutes difference = " + diffMinutes);
    System.out.println("diffHours difference = " + diffHours);
    System.out.println("diffDays difference = " + diffDays);
}

Instead of passing a Date to daysBetween, pass a long. You can get the current time (since Jan 1 1970) from a Calendar using getTimeInMillis(). Your code will now look as follows:

void printAppointment(Appointment a) throws ParseException {
    System.out.println(a.getSummary());
    System.out.println(a.getDescription());

    System.out.println(formatter.format(a.getStartTime().getTime()));
    System.out.println(formatter.format(a.getEndTime().getTime()));
    System.out.println(a.getAppointmentGroup());
    System.out.println(a.getLocation());


    System.out.println("Days difference = " + daysBetween(a.getStartTime().getTimeInMillis(), a.getEndTime().getTimeInMillis()));
}

private int daysBetween(long t1, long t2) {
    return (int) ((t2 - t1) / (1000 * 60 * 60 * 24));
}