datetime: How to get diff between 2 dates in month units?

[Pettersen, Bjorn S]

> From: python at sarcastic-horse.com [mailto:python at sarcastic-horse.com] 
> 
> Hi-
> 
> 
> I have a lot of monthly time series data.  I need to be able 
> to compare two dates and get the number of months that they are apart.
> 
> The datetime module is a daily-frequency data type.  It has a 
> timedelta
> object that returns the difference in days between two dates:
> 
> >>> d1 = datetime.date(2002,1,1)
> >>> d2 = datetime.date(2001,12,1)
> >>> diff = d1-d2
> >>> diff.days
> 31
> 
> I want to be able to compare monthly-frequency data, so that I can do
> something like this:
> 
> >>>firstdate = newMonthlyDatetime(2002, 5)
> >>>Nov2002 = newMonthlyDatetime(2002, 11)
> >>>diff = Nov2002 - firstdate
> >>>diff.months
> 6
> 
> Does anyone have any suggestions about how to do something like this?

No, but I do have one question..: would diff.months be valid given d1
and d2 above (which also contain a day part)?

If so, what would it be given the dates 3/1/2001 - 1/30/2001; i.e. is a
month 1/12 of a year, or until the same day next month (with special
rules for end-of-month)?

If you answer no to the first question then your very close to a (year *
100 + month) representation...

-- bjorn
(time series data is fun ;-)