> If the way you measure time takes leap seconds into account, you have no way of saying "exactly X Système international seconds from now". Note that this is

> If the way you measure time takes leap seconds into account, you have no way of saying "exactly X Système international seconds from now". Note that this is the case for anyone using POSIX time, which inherently assumes that hours start on multiples of 3600, and has to be adjusted or smeared when a leap second happens. But I've never seen a system that follows your recommendation, using TAI as the internal time and something like TAI-5:00:36 as the local time, except for GPS devices.