The relation between treating-as and seeing-as is not straightforward
Coordinated universal time (UTC) is the time scale used all over the world for time coordination. It was established in 1972, based on atomic clocks, and was the successor of astronomical time, which is based on the Earth’s rotation. But since the atomic time scale drifts from the astronomical one, 1-second steps were added whenever necessary. In 1972 everybody was happy with this decision. Today, most systems we use for telecommunications are not really happy with these “leap” seconds. So in January member states of the International Telecommunications Union will vote on dropping the leap second. (…)
We are using a system that breaks time. The quality of time is continuity. This is why a majority in the international community want to change the definition of UTC and drop the leap second. (…)
It was agreed some years ago that we should not think of any kind of adjustment in the near future, the next 100 or 200 years. In about the year 2600 we will have a half-hour divergence. However, we don’t know how time-keeping will be then, or how technology will be. So we cannot rule for the next six or seven generations.
