When using the Calendar class in Android Java the default start of the week is Sunday. To change this use the following function setFirstDayOfWeek
Calendar cal; cal.setCalendar(Calendar.getInstance()); cal.setFirstDayOfWeek(Calendar.MONDAY);
cal.getInstance() set it to the current date.
setFirstDayOfWeek takes an integer. Calendar.MONDAY is just an integer value of 1. Sunday has the value 0, Tuesday = 2, Wednesday = 3, Thursday = 4, Friday = 5 and Saturday = 6
To get the week number from Calendar you can do this:
String weeknr = String.format("%d", cal.get(Calendar.WEEK_OF_YEAR);