Combine GROUP BY and ORDER BY statement together

Date x y

1/8/05 3 23
2/2/05 232 223
5/8/05 34 234
4/12/05 56 435
6/1/05 345 235
5/2/05 56 878

my table is like this, now i would like to group the date by work week so all the fidure will add up according to work week and i want my date order by ascending.

what i aspect my result is

work week x y

1 345 235
5 90 1112
31 37 257
49 56 435

Do anybody have any idea on how to write this statement?