The pop-up calendar is a completely different type of calendar used on a Web site. Although it is quite different from the perpetual calendar, much of the code used to create it is nearly identical to the code you used for that calendar.
Here are some ways in which an online pop-up calendar is different from a perpetual calendar:
A pop-up calendar is displayed in its own window.
After a user selects a date, the pop-up window closes and fills in a field on the parent window.
No events are can be displayed in the calendar.
Just like with the perpetual calendar, display and rotation are two basic functions of the popup calendar. Luckily, getting and setting events is not an issue with this type of calendar. This time around, though, you'll have to worry about inter-window communication between the calendar and its parent window.