Why does my Excel 2010 Cell Format automatically change to Date Format every time I reboot my computer? I encountered a similar bug like this when our company upgraded from Excel 2007 to Excel 2010. Before the upgrade, everything was working just perfectly and I never had issue with it.

Well, the solution to this problem is very simple BUT I am not sure though if this is exactly the same FIX for everyone else out there. In my Excel 2010, I found out that my Cell Format will automatically change to Date Format the following day after I shutdown my computer after work and not every time I reboot it. I’ve tried closing the file and opening it again on the same day but the bug  WON’T appear. It’s really weird. 😀

It is really annoying hence it affects every sheet on excel file thus I need to change the format every time I opened the file the next day. Not to mention that all your data’s are messed up especially when you do some formula & reference. And NO, there are no MACRO’s running on my Excel.

So, What is the solution to this EXCEL 2010 Cell Format Auto Change to Date BUG?


  1. Go to HOME -> Click the Format -> Format Cells (Or use shortcut key Ctrl+1)
  2. Under Category -> Choose Custom ->Scroll down to the bottom and delete the funny code like these [$-4089] dd.
    (Note: Every computer will display different #-code so just delete these weird code [$-any number])
  3.  And Viola! That’s it. 😀

Excel 2010 Cell Format Automatically Changed to Date Everytime I Restart

Please let me know if the above solution for the “Excel 2010 Cell Format Auto Changed to Date Bug” doesn’t work. Or if you have some other fix to solve this problem, please leave a comment and share your knowledge. Thanks!