How Should I Store Dates in MySQL?

[eluser]TerryT[/eluser]
I am using JQuery's datapicker for users to pick the date of an item on my forms. My question is what is best practice for the format for storing dates in a mySQL table from a Codeigniter app?

I will be using the dates to determine items within the last 7 days and printing them on reports in dd/mm/yy format. Thanks.