Code:
select * from testdate where
(
((year(SaleDate )-1)*365)+
(month(SaleDate )-1)*30+
(day(SaleDate ))
)
<
(
((year(getdate())-1)*365)+
(month(getdate())-1)*30+
(day(getdate()))-30
)
its not perfect, but its close this will return the dates that are about 30 days old. its all in MSSQL so you'll have to convert it to your flavor of SQL