[LEAPSECS] Notation for transmitted vs. paper time scales

[Gerard Ashton]

There was some discussion of transmitted vs. paper time scales. For example,
it was implied that in 2014, one could derive TAI(NPL) by adding 35 seconds
to UTC(NPL). But NPL transmits its realization of UTC to the public,
presumably it is this transmission that is denoted by UTC(NPL). Let us
suppose a large interest payment was due 24:00 UTC on a certain date, and
the best available evidence indicates it was paid 23:59:59.99999 UTC(NPL).
But later it is determined that UTC(NPL) was 20 ns slow at that time, so the
corresponding UTC was 00:00:0.00001. So is it fair to change an on-time
payment to a default based on corrections that were not available at the
time the payment was made?

The point is that if someone is required to obey a law or satisfy an
obligation by a certain time, the time of performance of the required action
must be labeled with the civil time of the jurisdiction as made available in
real time in the jurisdiction. Paper adjustments later to the timescale are
not acceptable. Notations should allow one to distinguish between
contemporaneous labels vs. labels that may have been adjusted after the
event.

One might argue that UTC(NPL) designates a contemporaneous time label.
TAI(NPL), on the other hand, is not a label used by officials,  so its
status as contemporaneous or adjustable is undefined except in the mind of
some private individual that decided to use the notation.

Gerard Ashton