On Tuesday 27 September 2005 04:51 am, Robert Klemme wrote:
> No, I mean because of the underlying model (our calendar).  Months have
> different lengths.  Same for years and quarters.

Two thoughts, which I don't know whether will help or hurt (may be useful 
approximations?):

   * (I guess this is the furthest off point): There seems to be an at least 
"semi-official" designation of the weeks in a year--you will find some 
calendars that number the weeks, and when I've checked, those numbers seem to 
be consistent between calendars, even made in different countries.  (I think 
the ones I've noticed, some years ago, were calendars from England, Austria, 
and the US.)

   * Depending on the level of precision I wanted, I might calculate an 
interval in weeks, then consider 4 1/3 weeks ~= 1 month, 13 weeks ~= 1 
quarter, and 52 weeks = 1 year.  If I wanted to express some arbitrary number 
of weeks in months, (e.g., 62, I'd divide by 4.34 and round off to the 
nearest integer and call it that number of months.  

Nope, I take that back.  I'd more likely just express the difference between 
say, Jan 3rd and Dec 15 as the difference in months then the difference in 
days, i.e., 11 months, 12 days.  (and I'd approximate that as either 11, 11 
1/2, or 11 months, 2 weeks).

If I wanted to express that in weeks, I guess my two choices would be to use 
the semi-official designation of weeks (first bullet above) and get the 
number of weeks by the difference in week numbers, and then depending on the 
days of the week, approximate it to the nearest 1/2 (or actual number of 
days).

Or, calculate the actual difference in days, then divide by 7, call that 
weeks, and the remainder in days (or rounded off to, say, 1/2 week.

Do others see the need for other approaches?

Randy Kramer