ElapsedTime

Elapsed time is the amount of time that has passed between two moments. It represents a non-negative duration and is used to quantify how long a process takes, how long since an event occurred, or how much time remains until a deadline.

Calculation typically relies on two timestamps: a start time and an end time. Elapsed time equals end_time minus start_time. When expressing results, units such as seconds, milliseconds, minutes, or hours are common, and durations may be formatted as hh:mm:ss or in ISO 8601 duration form (for example, P0DT2H30M indicates two hours and thirty minutes).

In programming and systems contexts, elapsed time is often measured using timers that avoid calendar changes. A monotonic clock is preferred for interval timing because it is not affected by clock adjustments, time zone changes, or daylight saving time. If wall-clock time is used, care must be taken to handle potential anomalies such as clock skew or negative results when clocks move backward.

Common considerations include clock resolution, leap seconds, and the distinction between elapsed time and wall-clock time. Elapsed time measures duration, while wall-clock time refers to calendar time as seen on a clock. Proper representation and measurement are important in performance profiling, athletics, event logging, and project scheduling, among other applications.