Re: How to represent a calendar month as a field in django models

Hi Erik,

Thanks for your reply.

I'm aware of the problems with timedelta(months=2), since the length of a month is not fixed, a length of time specified in months is ambiguous. Though months do have an internally consistent algebra as you point out and people often refer to time-periods in month without any real-world confusion. I agree it is possible to create a class modelling this behaviour.

The downside to creating a new classt, is that all the existing date-related functionality in the standard library and django is lost and has to be rewritten or wrapped somehow.

I think I'll just have to look at my use-cases and pick the option that most easily facilitates those uses.

Cheers,

On Mon, May 4, 2015 at 2:30 PM, Erik Cederstrand <erik+lists@cederstrand.dk> wrote:

> Den 04/05/2015 kl. 14.21 skrev Erik Cederstrand <erik+lists@cederstrand.dk>:
>
> class Month(models.Model):
>    year = models.IntegerField()
>    month = models.PositiveSmallIntegerField()
>
>    def add_months(self, n):
>        assert n >= 0
>        dy, dm = divmod(self.month + n, 12)
>        self.year += dy
>        self.month += dm

Sorry, that's supposed to be:

    def add_months(self, n):
        assert n >= 0
        dy, self.month = divmod(self.month + n, 12)
        self.year += dy


Disclaimer: This possibly only applies to the Gregorian calendar. Read up on the others as needed: http://en.wikipedia.org/wiki/List_of_calendars :-)

Erik

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