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That's the date the track was added to your library first time, and it's stored in MB database only. So it's different from date created and date modified.
The file was not the same file as the one in your library if you look at its creation date. Looks like you made a copy and imported it to the library (and maybe replaced the original with it).
If you had dragged or used Folder (Move) command, it wouldn't have happened.