Unix Timestamp

A Unix timestamp counts elapsed time from 1970-01-01T00:00:00Z. Systems commonly store seconds, milliseconds, or occasionally microseconds, so the unit must be known before conversion. The value itself has no timezone; timezone enters when a client formats the instant for display. This makes timestamps useful across services, provided every system agrees on precision and serialization rules.

Check the number of digits and the API contract before assuming seconds or milliseconds. Compare the converted UTC value with a known event, then display it in the operator's timezone only as a presentation choice. Watch for zero values, negative pre-epoch dates, integer overflow, and strings that contain timezone offsets already. When debugging, record both the raw timestamp and the formatted ISO 8601 value so a later reader can reproduce the conversion.

A timestamp is small and deterministic, so local conversion is faster and keeps incident logs or identifiers out of a remote service. It also avoids the confusion of a server's default timezone. The utility cannot correct a producer that used the wrong unit or clock; use it to identify the mismatch, then fix serialization and time synchronization at the source. Store instants in UTC and localize only at the user interface.