I have a problem with a date formula in a spreadsheet that I would very much appreciate help with. It seems that the formula doesn't work past the new year for some reason. My formula is set as follows:
Cell Z3 has a date on it, cell AA3 should populate with a future date 4 weeks from now. My formula is =IF(Z3="","",Z3+7*4). This works as long as the future date doesn't go past the new year. If the date is for 2018, it gives #VALUE as a result.
"...Could it be because it's Excel online? ..."
I do not think it would make any sense if it happened.
It is a basic operation.
And you're using EXCEL, with the only difference being the online version.
Did you try to open a new worksheet and do the same test?