> No. Whenever it comes up for discussion, you can't get any two
> people to agree on when "week 1" should start.

Yes, I understand your point, but , when I read
http://tracker.firebirdsql.org/browse/CORE-663

I agree with ..."should implement the ISO standard like other DBMS
have. "

1. This function is useful

2. Other DBMS support this feature
- MS SQL has DATEPART('week',d)
- MySQL has WEEK(date[,mode]) mode solves problem you mention
plus WEEKOFYEAR() which is same like WEEK(date,3) it seems like
ISO8601 compliant
- PostgreSQL has extract(week from d) ISO8601 compliant

3. At least add week() to fbudf, when extedning extract() is not
acceptable

4. It is better having week() function, which satisfies 50% of users,
than absolutely no one