Oops! The previously formula fails for the 11th, 12, and 13th. Use
this instead:
=(IF(INT(DAY(A1)/10)=1,DAY(A1)&"th",IF(MOD((DAY(A1)),10)=1,DAY(A1)& "st",IF(MOD((DAY(A1)),10)=2,DAY(A1)&"nd",IF(MOD((D AY(A1)),10)=3,DAY(A1)&"rd",DAY(A1)&"th")))))&TEXT( A1,"
mmmm ")&YEAR(A1)