Viikkonumeroiden korjaus

Oletuksena MySQL käyttää viikkonumeron laskennassa modea 0: 

    Week 1 is the first week with a Sunday in this year. 
    First day of week Sunday. Week range 0-53.

Vaihdetaan käyttöön mode 3: 

    Week 1 is the first week with more than 3 days this year. 
    First day of week Monday. Week range 1-53.

http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_week