| ### Decide on course for historic data

If you are not using windowing, you need to decide how to handle your historic data. If you are bound by some constraint to make no changes to them, your "choice" would be 2.:

1. Expand or compress all old files and databases or
2. Keep copies of old data, in which case you need to decide whether to:
   1. Keep copies of old code to access the data or
   2. Your code needs to handle both 2-digit and 4-digit year
      Could use condition bridges when accessing old data

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