Originally posted by Lil Puppy:

One of the pieces of information is the Created: entry. It has the exact date and time it was created. This is when you made that save.

Nope. If Valheim were to only ever EDIT the world save game files instead of writing new ones and renaming the old ones to "*.old" you'd be right but I'm reasonably sure Valheim works like that...
At least none of my worlds has the real original creation date.