Converting a date to a specific numeric value.

I want to change a date, 3-Jan-12 (format), to a table reference so that any date in each particular month will arrive at the corresponding number adjacent to it in the table shown below. For example, 3-Jan-12 = 0, 4-Feb-12 = 1 and so on. The table below is on a separate sheet called arrays, with the data in rows L and M respecively. The original date is in cell D2 and continues down column D. Can anyone assist? Even if the outcome is provided on as a single sheet reference I can update the other sheet name ok.

Month Month_Value
January 0
February 1
March 2
April 3
May 4
June 5
July 6
August 7
September 8
October 9
November 10
December 11

if the months are in order you can use
=index('other sheet'!$B$2:$B$12,month(D2))