I don't know but here weeks "start" on monday. So that's the order i Place the checkboxes in where you can check on which days you want to place something on the calender (can do this biweekly etc for x weeks), but by default sunday = day 0 and not monday. This is really anoying to work with. I saw some stuff about firstdayofweek with calenders but nothing to set it as a general setting for my application. Is there anyway to tell ASP.net to start with monday as day 0 ?