Re: ISO weeknumbers
Date: Mon, 5 Jan 2009 13:36:12 -0800 (PST)
On Jan 5, 12:41 pm, "Terry Dykstra" <tddyks..._at_forestoil.ca> wrote:
> The IW format string returns the ISO week number
> Week of year (1-52 or 1-53) based on the ISO standard.
> I'm confused by this. When would you get week 53? For example, when
> running this against the last week of 2008 (using 126.96.36.199 SE) , it switches
> from week 52 to week 1 while still in December.
> select to_char(to_date('20081228','yyyymmdd') ,'IW') from dual;> 52
> select to_char(to_date('20081229','yyyymmdd') ,'IW') from dual;
> > 01
> Terry Dykstra
"The first week of a year is the week that contains the first Thursday
of a year."
http://en.wikipedia.org/wiki/ISO_week_date "If 1 January is on a Friday, Saturday or Sunday, it is in week 52 or 53 of the previous year. 28 December is always in the last week of its year."
See metalink Notes:179534.1 and 238676.1.
So this year, Thursday was the new years day, and going back to Monday is in 2009. Next year, it will be on a Friday, so this year, 2009, will have 53 weeks. This is confusing enough I almost thought you had a bug!
SYS_at_10.2.0.4 > select to_char(to_date('20081231','yyyymmdd') ,'iyyy/ IW') from dual;
SYS_at_10.2.0.4 > select to_char(to_date('20091231','yyyymmdd') ,'iyyy/ IW') from dual;
-- _at_home.com is bogus. Polar Express: http://new.dailyexpress.co.uk/posts/view/77987/Received on Mon Jan 05 2009 - 15:36:12 CST