Numbers constantly changing to Dates

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?

Have you tried to change the cell to "General"

You can do calculations in General Format.

The format of the cells are in GENERAL; however, when I reopen my workbook, it goes back to DATES even though I never changed it to dates before.

You can set your Format to a Number format or a General format. The number format will ask you to set your decimal places and you are also able to add in the "," as a separator. Make sure to click on the column (A, B, C etc) to so you don't have to change it for each cell. I've had times when excel looked at a cells format set as text and converted it to a date. Changed the format and it fixed my problem. Hope that helps.

I will tried that in a bit and observe it for couple days and see what happens.

If I am typing in data I can change the format from general to something other than date to prevent Excel from automatically assuming that I want dates shown. However, if I am cutting and pasting data that has fields that are in a format that Excel thinks represents a date, for example 3/30, but I really just want to show it as a text fraction, there seems to be NO way to prevent Excel from automatically reformatting the cells to general and assuming that it represents a date. Then there is no way to revert the data back to what I originally pasted. My only option seems to be completely retyping any data to which Excel does this. I can't seem to find any way to stop Excel from automatically assuming that I want something to show as a date in these cases.