>>>They both wrong and both right because they use there own definition of the WEEK(). See http://www.windowsitpro.com/SQLServer/Article/ArticleID/14340/14340.html, for example.
>>>
>>
>>I don't agree.
>
>You may not agree, but a standard is a standard, and the international standard is that week 1 is the first week of the year to contain at least four days.

This is incorrect because insufficient for a definition:
ISO-FDIS-8601.pdf

A calendar week is identified within a calendar year by the calendar week number.
This is its ordinal position within the year,
applying the rule that the first calendar week of a year
is the one that includes the first Thursday of that year
and
that the last calendar week of a calendar year is the week immediately
preceding the first calendar week of the next calendar year.

Without the second condition, the first is ambiguous.