wallet::CWalletTx::nTimeSmart

Stable timestamp that never changes, and reflects the order a transaction was added to the wallet. Timestamp is based on the block time for a transaction added as part of a block, or else the time when the transaction was received if it wasn't part of a block, with the timestamp adjusted in both cases so timestamp order matches the order transactions were added to the wallet. More details can be found in CWallet::ComputeTimeSmart().