How to convert integers representations of a date to a date format variable

Hello All, I would like to convert integers like the day, month and year to a date representation to store it in a session variable. There's a form where the user posts day, month and year. So then I run checkdate($month,$day,$year) and make sure the date is valid. So, let's say I have 12 for month, 30 for day and 2001 as year. Do I have to create a timestamp? How to create a TimeStamp? I need to store it as 30/12/2001 (but not a string) not only on a session variable but also to make it easier to work with a MySQL table. After that I want to play with it as a string so I will use the date() function, that's why it is important to save it as a validade date format value. Any sugestions? Thank you in advance, Carlos Fernando. Linux User #207984