Weekday name not matching with current day of month

[assembleMHN]

Hi guys, i really hope some of you can help me out, im having a weird issue with the calendar view where the name of the day of the week dont match the day of month. For instance here is october:

As you can see the first of october shows as saturday, but i is infact friday. Im not sure why the entire calendar has shifted a day, does any of you know how to correct this?

Best Regards
Morten