date probelm in excel

[kristian032911]

hi! i am new to this forum and i hope you can help me with my problem. i am using excel to create 8 groups that does night shifts for 4 days then another group does it afterwards and so on. instead of putting the dates manually and adding 4 days after the start of each night shift, is there a way or a formula i could use to just make it easier so that i wont be able to just manually do the dates each year? i've put a screenshot copy of the excel file that i am working on so that u guys can see what is my problem. thank y0u very much!