Tag Duration

Duration

timescale: handling the influence of leap seconds

Section 4:

A duration is the length of an interval of time. Durations in this format are given in SI seconds, possibly adjusted for conventional corrections of the timescale given (e.g., leap seconds).

That means that a duration describes the difference in timestamp according to the timescale specified.

In the UTC (Posix) timescale, every day is 86400 seconds long. Any duration in this timescale rests (or skips) during a leap second.

This is fine for references to civil time, but not for durations that need to map to physical processes (such as the movement of a pendulum, or switch-on times of a physical process such as a heater, etc.). To avoid a leap second leaving the heater on for too long, such durations should use the timescale TAI.

Example to switch on a heater for 3 seconds:

1002(      # duration
  { 1: 3,  # 3 SI seconds
    -1: 1  # in real time (timescale = TAI)
  }
)