A timestamp is a string that indicates the date, time, and time of an event. In a narrow sense, it refers to the postal stamp that is stamped on mail to indicate the date and time of mailing (see image). Nowadays, the term "timestamp" is well known in computers.

A timestamp recorded by a computer, digital camera, or other electronic device (also called a "digital timestamp" to distinguish it from other things) does not refer to the exact time an event occurred, but rather the time the event was recorded on the computer. In many cases, this difference is not important. However, if the difference between the time the event was recorded by the timestamp (e.g. the time the log was written) and the time the recorded event occurred is too large, there is a risk of discrepancies in consistency, so the difference should be as close to zero as possible.

ISO 8601 is a standardization of date and time representations. These standardized representations are often used to generate timestamp values.