Month/year support

[jd]

I see that its commented in the code, any reason for that?

[wroberts]

Months and years are periods of time directly related to the calendar; they could be included in pytimeparse, but only relative to a particular date (such as the current system time). There's also complications such as leap-years and leap-seconds. For the moment, I chose to only include time expressions which correspond to a fixed length of time.

minutes, hours, days: http://tools.ietf.org/html/rfc3339#section-2 weeks: http://www.tondering.dk/claus/cal/week.php#weeklengths

[jaraco]

There are use-cases where years/months support is useful even if not following a calendar, using nominal fixed lengths of time for each.

Consider the case where a user specifies an interval for expiration. For example, this cookie is good for "1 month" or delete all records older than "3 years". In these cases, being able to compare a timestamp or datetime against (now - interval) is useful, even if it's not going to be the same time on a wall clock or same day on the calendar.

For that reason, I've added months and years support to tempora's parse_timedelta function.

It would be useful in these cases if pytimeparse supported parsing months and years, either with a caution in the docs about what that means or even a UserWarning that an implementer may choose to suppress to acknowledge the potential pitfalls.

[jhtitor]

+1. This would be extremely useful for reasons @jaraco listed.

Had to fork pytimeparse just for that little uncomment. Please give this issue another consideration.

[Toldry]

@wroberts Could you perhaps add a flag to the module that enables using months and years that users must explicitly set in order for those functions to work?

e.g.

import pytimeparse
pytimeparse.timeparse.timeparse('3 months') # None
pytimeparse.timeparse.enable_imprecise_months_and_years()
pytimeparse.timeparse.timeparse('3 months') # 7884000

You could use the average length of a month (30.42 days) and the average length of a year (365.25 days) to make it slightly more precise for general usage.

It is worth noting that that is what wolframalpha.com does:

https://www.wolframalpha.com/input/?i=1+month+to+seconds