Get data using user selected date

[ghjk]

I'm developing web site using php and mysql. In there user has to select a date, and data belongs to that date should print.My date field type is datetime.
This is my code and it is not working.Could you please help me?
GDate-> user selected date

[PHP]SELECT Rainfall,Date FROM rainfall WHERE CAST(Date as DATE)='$GDate' AND SID='$GSID'[/PHP]

[ronverdonk]

Depends on the format of the date in the $GDate variable. It should be YYYY-MM-DD.

Ronald