Change From a Date Format
Likely the solution to your problem is to select the formatting option of “Plain text.”
Notice that when you type a number into a spreadsheet cell it aligns right. Text aligns left. Notice in the example below the 3 number values are to the right of the cell and the words I typed are to the left.
Changing numbers as text to a number converts it to DateValue. If you’re scratching your head on that one, good news! DateValue is not something you need to know! If something wacky like this happens just use Control Z (undo) to put it back and change it to “Plain text.”
Long Story Short
Format to Plain Text and probably your date problems will be fixed!