Assuming CREATED_DATE is a field of type date, you have a data type problem. "12/1/2010" is interpreted by FileMaker as text, not the single integer that is actually stored as a "date" in a date field.
CREATED_DATE ≥ GetasDate ( "12/1/2010" ) and CREATED_DATE ≤ GetasDate ( "12/31/2010" )
is one option.
CREATED_DATE ≥ Date ( 12 ; 1 ; 2010 ) and CREATED_DATE ≤ Date ( 12 ; 31 ; 2010 )
There are also other calculation that can be used to identify all records with a date that falls in a given month as well as several different find requests you can use to find dates for given to find all records of a given month.
This worked perfectly! I also learned something new. Thank you.