So I'm having some issues in trying to do this, I already tried with this code:
thatDay.set(Calendar.DAY_OF_MONTH,25);
thatDay.set(Calendar.MONTH,7); // 0-11 so 1 less
thatDay.set(Calendar.YEAR, 1985);
Calendar today = Calendar.getInstance();
long diff = today.getTimeInMillis() - thatDay.getTimeInMillis(); //result in millis
And I kinda know why this is not what I want because, the thing that I need is taking the first date that I insert in database, and I want that to be like (CURRENTDATE - TXTDATE == DAYS THAT LEFT)