"Date object"

Hi, A bit confused, I downloaded a function and it says it takes a "date object"....what exactly is a "date object"? This is exactly what is written " The function takes a date object as its only parameter." I checked out the manual and tried a timestamp, and then checked "date", "getdate", "mktime" etc am doing something wrong...but wont know what till I understand the "date object" that this needs. The script is at: http://scripts.franciscocharrua.com/php-calendar.php Thanks, -Ryan