Date Query

Hi all:

I am trying to get data that wasn't used in the last six month. Created_on (date field)

select Category_tree_value, Created_on from workitem
where Created_on (field was used from the last six months)

Created_on format (2005-10-01 00:00:00.000)

Thanking everyone in advance.

LystraTry

where Created_on < DateAdd(Month, -6, GetDate())