The WEEKW
w. informat reads the week-number value within
                  the year. If the input does not contain a year expression, the WEEKW
w. informat uses the current year as the year
                  expression, which is the default. If the input does not contain a
                  day expression, the WEEKW
w.
                  informat uses the first day of the week as the day expression, which
                  is the default. Algorithm W calculates the SAS date value using the
                  number of the week within the year (Monday is considered the first
                  day of the week). The number-of-week value is represented as a decimal
                  number in the range 0–53, with a leading zero and maximum value
                  of 53. For example, the fifth week of the year would be represented
                  as 05.
               
 
               The inputs to the WEEKW
w. informat are the same date for the following
                  example. The current year is 2012.