Date range to division

Hello,
we capture birth date as date and we would like to convert to division

Month/Year 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
January U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
February U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
March U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
April U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
May U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
June U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
July U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
August U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
September U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
October U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
November U18 U17 U16 U15 U14 U13 U12 U11 U10 U9
December U18 U17 U16 U15 U14 U13 U12 U11 U10 U9