I have a spreadsheet that takes a start date and calculates the date that a
recertification is due. There are 4 certification periods 90days, 90days,
60days and 60days. My current formula looks something like this B2=A1+89,
C2=B2+90, D2=C2+60.

This has been working fine except that Excel is considering February has 30
days vice 29, is there a way to fix this?

Or to make the process simplier?

Any help would be gratefully accepted.