I have been using my spreadsheet for couple months now and never experienced this issue, but recently my numbers ( 1, 2, 3, 4, etc) are converting to dates.
As well, one of my co-workers (different city, different spreadsheet) is experiencing the same issue, when he reopens his workbook all his numbers are dates.
This is very annoying and I CAN'T change my numbers to TEXT, or put a ' in front my numbers as these are fields people enter information or these fields are used for calculation.

Is there a fix?
Is this an excel issue?