Datetimetimedelta

Datetimetimedelta is an ISO‑8601 compliant string representation that describes the duration between two points in time. It expands upon the traditional datetime format by allowing optional minutes, seconds, and fractional seconds, separated from the date component with a 'T'. The format follows the pattern -P[n]y[n]m[n]dTh[n]h[n]m[n]s[n]fraction, where the leading minus sign denotes a negative duration.

Unlike a raw datetime value, a datetimetimedelta expresses a difference rather than a fixed instant. It is often used in contexts such as time-tracking, scheduling, and data analysis where the length of an interval matters. In computing libraries like Python’s datetime module, pandas, and SQL standards, the type is supported as both a native object and a string expression. Converting from a datetimetimedelta to seconds or milliseconds is straightforward, enabling arithmetic operations such as addition, subtraction, or scaling by a scalar.

Historically the ISO‑8601 duration format was introduced to unify various duration specifications across systems. The datetimetimedelta sub‑standard provides a granular definition that aligns with the precision of most modern timekeeping devices. Because of its widespread acceptance, many APIs and data interchange formats like JSON Schema and XML Schema use datetimetimedelta to represent relative time spans.

When parsing or generating datetimetimedelta strings, it is essential to handle sub‑second precision accurately and preserve the sign of the duration. Proper validation tools reject malformed tokens like missing units or duplicate components. In many programming environments, the built‑in duration type will automatically serialize to the ISO‑8601 representation, ensuring consistency across different platforms.