weeks duration (and other duration) use of decimal value

[aphillips]

http://w3c.github.io/sdw/time/#time:weeks

The property weeks duration is counted using a decimal value, so one can specify 2.5 weeks. A (Gregorian) week is 7 days, so I suppose that "2.5 weeks" is 17.5 days? Other properties like months duration here are less clear, since months often have different numbers of days. Should the decimal value be more clearly defined?

[dr-shorthair]

I will add note on the GeneralDurationDescription class warning that the exact duration

• depends on the temporal reference system
• for months is imprecise for calendars where the length of a month varies.
  the latter also on the DurationDescription class.

[dr-shorthair]

Note added to GeneralDurationDescription

The exact duration of a duration expressed as a GeneralDurationDescription depends on the Temporal Reference System. In some calendars the length of the week or month is not constant within the year. Therefore, a value like "2.5 months" may not necessarily be exactly compared with a similar duration expressed in terms of weeks or days. When non-earth-based calendars are considered even more care must be taken in comparing durations.

Note added to DurationDescription

In the Gregorian calendar the length of the month is not fixed. Therefore, a value like "2.5 months" cannot be exactly compared with a similar duration expressed in terms of weeks or days.

[chris-little]

Suggest simplifying text to start: "An exact duration expressed as a GeneralDurationDescription". I do not think it alters the semantics.

[dr-shorthair]

Whoops - of course