Weeknum


 * WEEKNUM
 * week number
 * date to week number
 * ISO-8601
 * test sets
 * 2005-01-01 → 53
 * 2005-01-02 → 53
 * 2005-12-31 → 52
 * 2007-01-01 → 01
 * 2007-12-30 → 52
 * 2007-12-31 → 01
 * 2008-01-01 → 01
 * 2008-12-29 → 01
 * 2008-12-31 → 01
 * 2009-01-01 → 01
 * 2009-12-31 → 53
 * 2010-01-03 → 53

Excel

 * number
 * text (leading 0)