Excel – How to stop numbers converting to date format on copy paste in Excel

This happens if you open each Excel file in a separate instance of Excel, i.e., if you start Excel as a new process for each file. The easiest solution is to use the "file" (logo)/"open" option inside Excel.

you could always try writing a macro for that. excel has a really nice macro recording tool that you could use too, and then just run it as needed (provided you make some changes first of course to the program)

dim firstLetter as String 
dim secondLetter as String 
dim firstNumber as integer 
dim secondNumber as integer 
dim firstReference as string 
dim secondReference as string 
dim contents as string 
firstLetter = inputbox("Where's the first column? (it's letter)") 
firstNumber = inputbox("And what's the first row? (just the number)") 
secondLetter = inputbox("What column is this going to be moved to? (the letter only.)") 
secondNumber = inputbox("And what row? (the number.)") 
contents = range(firstletter + cstr(firstnumber)).formula 
range(secondletter + cstr(secondnumber)).formula = contents