Generating and Confirming Timestamp on P2P Network

Generating and Confirming Timestamp on P2P Network

I'm planning to code a P2P network. In this network each client can create
a record and share it with the others. You can think this like Bitcoin's
transactions. Generating the record and sharing it OK.
But, I want to add a timestamp on the record too, my problem is about
confirming the time stamp.
Each client can create a record with a timestamp but how can the others be
sure that this time stamp is correct? How to confirm that timestamp on the
record and records create time is the same?
Can you please give me a advice?