how to get Received Time of Transaction in validation.cpp bitcoin core for research purpose i needed Transaction hash,size, fee and received time. i have already managed to get hash, size and fee but unable to get time. what to do?
Transactions do not have a time. There is a time that your node received the transaction, but that is not necessarily the time that the transaction was originally broadcast.

To get the time of a transaction being accepted to your node's mempool, you can add debug=mempool to your bitcoin.conf file and then restart Core. Then grep through the debug.log file for any lines of the form "AcceptToMemoryPool: peer=%d: accepted %s (poolsz %u txn, %u kB). Since all lines have a time logged with them, you can get the time that a transaction was accepted to your node's mempool. However this will not include any transactions that are first received in a block.