When deciphering a coded date in Excel, there are a few things to keep in mind. The first is that the code is likely to be in one of two formats:
The second thing to keep in mind is that the code may be reversed, so it's important to check both formats. The third thing to keep in mind is that the code may be in a different language, so it's important to use a translation tool like Google Translate. Finally, it's also worth checking whether the code uses a different calendar, such as the Julian calendar.
Once you've kept all of these things in mind, you should be able to decipher the coded date in Excel. If you're still having trouble, there are a few other resources that can help: