Bugzilla – Bug 593
Week 53 is sometimes an error
Last modified: 2011-05-25 12:51:13 CEST
Some years (such as 2009) have a week 53, while others (such as 2008) don't. The value for <input type=week> must be a valid week string, which can only end in W53 for years with 53 weeks.
Validator.nu appears always to treat W53 as valid, regardless of the year; it should instead take the weekday of the first day of the year into account and only allow W53 if the year starts on a Thursday or is a leap year that starts on a Friday:
AFAICT, the code that tries to do the right thing ends up saying week 53 is always *invalid*.
It appears that ICU4J is broken:
Fixed by not using ICU4J:
I hope the fix is correct. I'm not fully confident that it is. However, it is correct per citationless claims on Wikipedia.