The Ledger will store a history of all operations, so you could scan through old operations and get a history of what the data values were.
I'm not sure how the data is stored in the postgres database that Horizon and stellar Core use. You may be able to get historical values with a SQL query if the value is stored as part of the operation record. If it's not, I think you'd have to write your own tool to read the ledger files.
