When interacting with Kaspa nodes for the purpose of interfacing a wallet, you are meant to use UTXO data structures. UTXOs allow you to track per-address balances and create outgoing transactions.
Kaspa nodes currently do not provide an RPC call to lookup transactions by their id (txid).
As such, while you do have txid reference in each UTXO, you do not have a way to get any additional transaction information via a direct RPC lookup.
The kaspanet.io web wallet, for the purposes of record-keeping, creates transaction records containing txids aggregated from UTXOs.
Transaction records can also be looked up externally using the Kaspa block explorer: https://explorer.kaspa.org/txs
Due to the inability to get transaction by id, you can not tell exactly when a transactions have occurred. UTXOs do not contain any timestamp data, as such, you can only estimate the transaction timestamp based on the time the wallet has observed the transaction.
There are plans for a new API call that will allow approximation of transaction timestamps using the DAA score. This is planned for after the initial release of the Rusty Kaspa.