Timestamp

A timestamp is a piece of data that records when something happened, usually as a date and time of day or as a count of seconds since a reference point, such as Unix time, which counts from 1 January 1970. Systems attach them to files, logs and transactions, normally in Coordinated Universal Time (UTC) to avoid confusion across time zones. In finance, accurate timestamps are needed to sequence trades, prove when payments were made and meet regulatory reporting rules. On blockchains, every block header contains a timestamp set by the miner or validator; Bitcoin accepts it only within limits relative to recent blocks and network time, so it is approximate rather than exact. Because blocks are linked by hashes, data recorded on-chain gains a tamper-evident proof of existence by a certain time, which is the basis of blockchain notarization.