posted January 07, 2006 08:45 AM            

------------------
Egbert Zijlema, journalist and programmer (egbert at egbertzijlema dot nl)
http://www.egbertzijlema.nl/programming.html
*** Opinions expressed here are not necessarily untrue ***

posted January 07, 2006 09:03 AM            

I seem to recollect that according to ISO norms, week 1 is the first week of the year that contains the first thursday of January.
Seems to be like that for 2005 and 2006.
I believe that's the reason that 2004 had 53 weeks. Atleast here in Belgium. Don't know about the rest of the world...

Kind regards

------------------
Eddy
email: raimundo4u at yahoo dot com
www.devotechs.com -- HIME Huge Integer Math and Encryption library--

posted January 07, 2006 09:56 AM            

I don't know about those countries, but in the USA it's an industry thing not a national thing. Some industries traditionally use one system, and other industries use another. For example I come from the TV/radio broadcast industry which defines months as ending on the last Sunday of the calendar month, and week numbers within months are necessarily defined by that standard.

ISO standards are wonderful but not everybody uses them.

-- Eric

posted January 07, 2006 10:01 AM            

This is correct.
But on my box Windows returns "week 1 is the week containing Jan. 1" (with the locale Dutch (Belgium) set).
Try the code that I published in the other thread.

posted January 07, 2006 02:29 PM            

I can't recall a circumstance where a meeting or shipping date
was defined as falling on the Wednesday of the 38th week of
the year, or anything similar. It's always the day within the
week of the month, or given date.

Obviously, anybody relying on Microsoft code to determine the
week number would likely be getting the same results. However,
if there is a variance from some outside reference, you can
add or subtract a value in Excel to make the two match, but I
don't know of any case where anyone had ever done this.

In fact, I don't know of any case where someone has used Week
of Day for anything beyond projecting the approximate date for a
shipment to arrive, or something like that. But even that was
unlikely since it was easier just to take the number count for
the date and add some offset, such as 30 or 60, and convert
that back to a date and say "on or about" in referring to it.

It might be a matter of interest, but seems somewhat unnecessary
if there is no pronounced need for this particular feature. I
don't think I will be giving it much thought in the future.

posted January 07, 2006 02:59 PM            

This is, indeed, very important, especially in countries where week numbers are printed on calendar sheets. What if every printing company would use its own rules in this respect? And, as a programmer, how can you produce a calendar with correct week numbers when a call to LocaleInfo returns the wrong values for
%LOCALE_IFIRSTWEEKOFYEAR?

The latter seems to be the case for Belgium. My Windows (XP Home Edition, Service Pack 1) returns 0 for that country, which means: the week that contains the date of January 1 is week number one. Which appears to be wrong, however. In practice, Belgian calendars are printed according to ISO 8601: Monday is the first day of the week and the week that contains the first Thursday of the year (or: contains at least 4 days) is week number one. Hence this rule, January 1 of this year belongs to week 52 of 2005.

Thank you very much Eddy Van Esch for checking this for me.

------------------
Egbert Zijlema, journalist and programmer (egbert at egbertzijlema dot nl)
http://www.egbertzijlema.nl/programming.html
*** Opinions expressed here are not necessarily untrue ***

posted May 19, 2006 09:47 PM            

From the link:

quote:

---

The .NET GetWeekOfYear() method will NOT produce correct ISO 8601 week numbers regardless of culture or CalendarWeekRule settings. Here is an explanation of the problem, as well as a custom method that does the right calculation.

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posted May 19, 2006 10:17 PM            

I was under the impression that Jan 1 is the day that immediately
follows Dec 31 of the previous year.

IMO: What difference does it make and who cares.

posted May 20, 2006 02:13 PM            

quote:

---

Originally posted by Mel Bishop:
I was under the impression that Jan 1 is the day that immediately
follows Dec 31 of the previous year.

---

quote:

---

Originally posted by Mel Bishop:
IMO: What difference does it make and who cares.

---

Kind regards

posted May 20, 2006 05:06 PM            

In the UK we only have 1 day per year

That's today