timesince - wrong results for 11 months + several weeks

[אורי]

Hi,

I'm using timesince to format how much time passed since the user last visited my website. The code is:

_("On {date} ({timesince} ago)").format(
    date=formats.date_format(value=last_visit_date),
    timesince=timesince(d=last_visit_date, now=today)
)

Now I created a test to test these times, and I noticed that for a year minus a week, the result is "(11\u00A0months, 4\u00A0weeks ago)" (why the "\u00A0" and not a space?), and for a year minus 2 weeks, the result is "(11\u00A0months, 3\u00A0weeks ago)":

                user_18 = ActiveUserFactory()
                user_18.profile.last_visit -= (relativedelta(years=1) - relativedelta(weeks=1))
                user_18.save_user_and_profile()
                self.assertIs(expr1={'en': "(11\u00A0months, 4\u00A0weeks ago)", 'he': "(לפני 11\u00A0חודשים, 4\u00A0שבועות)"}[self.language_code] in user_18.profile.last_visit_str, expr2=True)
                user_19 = ActiveUserFactory()
                user_19.profile.last_visit -= (relativedelta(years=1) - relativedelta(weeks=2))
                user_19.save_user_and_profile()
                self.assertIs(expr1={'en': "(11\u00A0months, 3\u00A0weeks ago)", 'he': "(לפני 11\u00A0חודשים, 3\u00A0שבועות)"}[self.language_code] in user_19.profile.last_visit_str, expr2=True)

Now, a year is 365 days, a year minus one week is 358 days, which is 11 months and 3 weeks. I think the problem is because each month is considered as 30 days, so 11 months are 330 days. But 11 months are about 334 days actually, so we receive a result of 11 months and 4 weeks, instead of 11 months and 3 weeks.

A fix would be to change the number of days in a month to 30.4 (the average), optionally only for more than 2 months (because it makes sense to calculate exactly 30 days for the first 2 months).