Dateadd command in SQL

This is very much straight forward but easily forgettable. "dateadd" command is a very useful command in queries. That's why i thought of adding this to my blog.

select dateadd(week,-3,getdate());

select dateadd(day,-21,getdate());

Ex:

select  * from dbo.tblMembership

where ValidTill >dateadd(week,-3,getdate());