DTV12 — the Convention du Metre is not a time interval

In DTV clause 11.2, the entry for Convention du Métre contains:

Definition: time interval of the signing of the Convention du Métre

Necessity: The Convention du Métre is at 20 May 1875.

These are inconsistent. The Necessity uses an undefined verb concept 'time interval is at time interval'.

It was intended that the Necessity uses 'occurrence is at (during) time interval'. The signing of the treaty is not a time interval; it is an event, an occurrence. The important fact is that the signing event occurred within the day, month and year denoted by 20 May 1875.

The conventions for establishing which time interval was named 20 May 1875 were established at that time by observation of noon at the Greenwich observatory. That was used as the basis for definition of Gregorian days until 1972, when it was replaced by Universal Coordinated Time (UTC). By convention, 24-hour periods with a midpoint at Greenwich noon might also be used to define Gregorian days before 1875, although actual approaches were different. Without specifying these conventions as well, the concept Gregorian day is not defined by the date of the Convention du Métre. There are several thousand distinct time intervals that encompass the signing of the treaty and have a duration of 86400 seconds.

The Convention du Mètre is intended to be an occurrence. Inaccurate references should refer to the Gregorian day of the signing, which is properly defined as the 24 hours beginning at midnight as determined by Greenwich Mean Time from 1884 to 1972 and by UTC thereafter.