SQL Get “ISO Year” for ISO Week

Question

I need to calculate the year a week is assigned to. For example the 29th december of 2003 was assigned to week one of year 2004 (this is only for europe, I think). You can t

Answer 1

DECLARE @date DATETIME
SET @date='2014-12-29'
SELECT 
CASE --Covers logic for ISO week date system which is part of the ISO 8601 date and time standard.  Ref: https://en.wikipedia.org/wiki/ISO_week_date
  WHEN (DATEPART(ISO_WEEK,@date) = 53) AND (DATEPART(MONTH,@date) = 1)
    THEN CAST((DATEPART(YEAR, @date) - 1) AS varchar(4)) + ('-W') + CAST (RIGHT('0' + CAST(DATEPART(ISO_WEEK,@date) AS varchar(2)),2) AS varchar(2))
  WHEN (DATEPART(ISO_WEEK,@date) = 1) AND (DATEPART(MONTH,@date) = 12)
    THEN CAST((DATEPART(YEAR,@date) + 1) AS varchar(4)) + ('-W') + CAST (RIGHT('0' + CAST(DATEPART(ISO_WEEK,@date) AS varchar(2)),2) AS varchar(2))
  ELSE CAST(DATEPART(YEAR,@date) AS varchar(4)) + ('-W') + CAST (RIGHT('0' + CAST(DATEPART(ISO_WEEK,@date) AS varchar(2)),2) AS varchar(2))
 END AS ISO_week