"transaction" shows the date/time at which the client received the block which contains the transaction, not the timestamp when the transaction made it into the block.

can be reproduced by sending bitcoins to a client that is offlne. later that client synchronizes the blockchain with the network and the transaction appears in the client with the date/time when the block was received and not with the time & date of the transaction reception by a miner (or block creation) as expected. that is inconvenient and confusing.

I searched the open/closed issues but could not find this one.
version affected 0.5 qt