unixtimestamp

A Unix timestamp, also called POSIX time, is a way to represent a specific moment in time as the number of seconds that have elapsed since the Unix epoch: 00:00:00 UTC on 1 January 1970. It does not count leap seconds. The timestamp is typically used in computing to encode instants in a machine-friendly form that is independent of time zones.

In its most common form it is a signed or unsigned integer representing whole seconds since the epoch. Some systems store sub-second precision using milliseconds, microseconds, or nanoseconds. The time_t type in C and POSIX interfaces is a widespread incarnation. Storage size varies by platform; 32-bit time_t will overflow in 2038 for many systems, leading to the Year 2038 problem, while 64-bit time_t avoids this for practical purposes. Some languages use floating-point seconds to preserve precision for high-resolution time.

Usage: Unix timestamps are widely used in databases, logs, and APIs to carry timestamps; they can be converted to human-readable dates in UTC or local time. Conversions and arithmetic are simple but care is needed with time zones and daylight saving adjustments. They enable efficient time comparisons and interval calculations in software systems.