Return the last saturday date regardless of when the sql was ran in any given week

Guys, I want to return the date of the last saturday regardless of when the code was ran.

ie today is 15/01/2015 so last saturdays date is 10/01/2015.

I want to run this any day of the week but the result has to be the same so when I run the code next week on say the 20/01/2015 the saturday to be returned is the 17/01/2015

Any Help

Thanks