DTV — Date-Time Issue - missing arithmetic on time point sequences

This issue was recorded in the final submission document, under the entry for "Gregorian month converts to time point sequence on the Gregorian days scale":
Issue: We have not defined arithmetic on time point sequences.

(The references in this text are to the beta-2 version of the specification.)

The verb concept ‘time point converts to time point sequence on time scale’ is used in 4 places in the specification. The similar verb concept ‘‘time point converts to time set on time scale’ is used in 3 places. We discuss each of these separately.

Descriptions are added to each of these glossary entries to help future readers understand them.

Clause 11.7

Gregorian year converts to time point sequence on the Gregorian days scale

The definition of this concept relies on normal everyday arithmetic, not on time point arithmetic. As discussed in clause 5.1, this specification uses but does not define ordinary arithmetic.

The definition fails to specify that the resulting time point sequence is a part of the Gregorian days scale. It is updated to make that clear. This requires a new verb concept ‘time point sequence is on time scale’.

Gregorian month converts to time point sequence on the Gregorian days scale
The definition of this concept relies upon the concept of adding a number to a time point sequence. This concept is entirely missing from the specification, and is added as a new verb concept ‘time point sequence2 is time point sequence1 plus integer’.

The definition claims to subtract ‘1 day’ from an index; it should be simply the number ‘1’. The definition is updated to fix these errors.

Clause 11.8
Gregorian month converts to time set on Gregorian year of days scale
The definition refers to a table with unstyled text. No change needed.

Clause 12.5
week of year converts to time set on the Gregorian year of days scale
The definition relies upon the verb concept ‘time point sequence2 is time point sequence1 plus integer’ that is discussed above, and on a verb concept wording that is an assumed Synonymous Form of the existing ‘time set1 is equivalent to time set2’ in clause 10.6. The verb concept and Synonymous Form are added.

This glossary entry requires no change.

weekday of year converts to time set on the Gregorian year of days scale
The definition has the same structure as the previous one, and requires no further changes.

Clause 13.4

hour of day converts to time point sequence on the day of seconds scale

The definition of this concept relies on normal everyday arithmetic, not on time point arithmetic. As discussed in clause 5.1, this specification uses but does not define ordinary arithmetic.

The definition fails to specify that the resulting time point sequence is a part of the day of seconds scale. It is updated to make that clear. This is another definition that requires the new verb concept ‘time point sequence is on time scale’.
minute of day converts to time point sequence on the day of seconds scale
As with the previous glossary entry, the definition of this one uses ordinary arithmetic but fails to state that the result is on the day of seconds scale.