Time - Wall Clock


Wall-clock time, or wall time is a duration that measure the time from the start to the completion of a task.


  • elapsed real time
  • real time
  • elapsed time

Wall-clock time is the time that a clock on the wall (or a stopwatch in hand) would measure as having elapsed between the start of the process and “now”.

Elapsed time may be negative due to:

  • leap second for instance if your process goes in millisecond
  • change in the OS clock if your function doesn't return a monotic time.

When using a non-monotonic clock source is to always check whether the elapsed time is negative.


In the context of a task being performed on a computer, wall-clock time is a measure of the real time that elapses from start to end, including:

  • time that passes due to programmed (artificial) delays
  • or waiting for resources to become available.

Wall-clock_time is is the difference between the time at which a task finishes and the time at which the task started.

Documentation / Reference

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