@TuomoT The cool thing about dates in Excel is that the are in fact numbers. So you can calculate with them. Assuming that 24.3.2021 is recognised as a date by your local Excel settings and the comma as the decimal separator, you can enter a formula like =A1+1,5. It will will add 36 hours (i.e. one and a half day) to whatever date/time is in A1.