SELECT ( CASE yourDate

WHEN 'January' THEN 1

WHEN 'February' THEN 2

WHEN 'March' THEN 3

WHEN 'April' THEN 4

WHEN 'May' THEN 5

WHEN 'June' THEN 6

WHEN 'July' THEN 7

WHEN 'August' THEN 8

WHEN 'September' THEN 9

WHEN 'October' THEN 10

WHEN 'November' THEN 11

WHEN 'December' THEN 12

END )

That should do the trick.