Suppose I have an ISO 8601 duration, expressed as "P1M". Phrased colloquially, this means "one month." Is there a standard rule for converting this into a number of seconds, assuming the start date is not known?
- For 30-day months, it might be 2,592,000.
- For 31-day months, it might be 2,678,400.
- In February, it might be 2,419,200 or it might be 2,505,600.
My gut says there's no way to resolve "one month" to an exact number of seconds without knowing context, and where those seconds are laid out on the calendar. But are there standard rules/conventions to calculate these durations in an abstract way?
From ISO 8601 documentation that I found (page 6 - http://xml.coverpages.org/ISO-FDIS-8601.pdf), it seems you are correct in that the number of seconds in a month cannot definitively be determined. However it does note that "In certain applications a month is regarded as a unit of time of 30 days", so depending on your application this may be a valid approach.
The distinction between "Calendar Time" (Years, Months, etc) and "Absolute Time" (Hours, Minutes, Seconds, etc) is sometimes an important one. As an example, some people might complain about having 13 mortgage payments some years if they paid every 30 days as opposed to every month.
来源：https://stackoverflow.com/questions/26265751/what-is-the-value-of-the-iso-8601-duration-p1m-in-seconds