Print milliseconds only (0 to 999)

I have worked a bit on the following code but still unable to print milliseconds (not all the millisecond from epoch time to user defined time). Where am I lacking to print remaining milliseconds e.g. If seconds are 30 exactly, milliseconds should be only 0. Milliseconds should not be more than 999 obviously.

    // Sets current date by default
    Calendar ob = Calendar.getInstance();

    // Sets user defined date with year, month, day of month respectively
    Calendar dob = Calendar.getInstance();
    dob.set(1990, 3, 25);

    // Want to get milliseconds only (0 - 999)
    long milli = dob.getTimeInMillis() - ( 60 * 60 * 24 * 30 * 12 * ( ob.get(Calendar.YEAR) - dob.get(Calendar.YEAR) ) );
    System.out.println(milli);

Why not do

long justMillis = dob.getTimeInMillis() % 1000;