Yeah, I suspect the wallet.dat file isn't a bitcoin wallet and loading a wallet from a different coin in bitcoin core will do strange things like that.
I've seen it happend with a friend a while ago.
I don't know about dates but it certainly showed bitcoin addresses and transactions too and none of them were in the blockchain.
Sounds like the same problem here..
Exactly this. You need to try loading this wallet.dat into the correct type of wallet - if not BTC, maybe try LTC or DOGE as suggested above.
Alternatively you could supply us with some of the txid's that the wallet has listed and we can all look for where it came from (simple parse of block explorers).
I did this recently with a different altcoin - tried loading it into my doge wallet and it had a ton of transactions, and eventually I learned it was from a totally different coin and the Doge wallet was trying to parse them.
Good luck.