Bruno Wolff III wrote:
>
> Shouldn't you be using 365.2425/12 (30.436875) for the number of days per
> month?
Well, ISO 8601 prefers "30" to some weird fraction when they
define the term "month"; and uses a different term "calendar
month" for the exact number of days in a known month.
They make a similar distinction between "day" which is
defined as "24 hours" and "calendar day" which includes
leap seconds, locally inserted & deleted daylight savings
time hours, etc.
None of this really matters because the SQL standard only
chose to import a couple definitions from ISO 8601 which
do not include "month" or "day".
But regarding the naming; it would be consistent with
iso 8601 if people wanted to make a distinction between
"months" and "calendar months".
http://lists.ebxml.org/archives/ebxml-core/200104/pdf00005.pdf
" 3.15 month unit of time of 28, 29, 30 or 31 days NOTE In certain applications a month is regarded as a unit of
timeof 30 days.
3.16 month, calendar time-interval resulting from the division of a calendar year in 12 sequential time-intervals,
eachwith a specific name and containing a specified number of calendar days
3.6 day unit of time of 24 hours
3.7 day, calendar time-interval starting at [0000] and ending at [2400] (which is equal to the beginning of the
nextcalendar day); typically a calendar day has a duration of 24 h [...] NOTE 2 The duration of a calendar day is 24
hours;except if modified by: — the insertion or deletion of leap seconds, by decision of the IERS, or — the insertion
ordeletion of other time intervals, as may be prescribed by local authorities to alter local time.
"