Here's a flexible, simple pop-up calendar written to work
across browsers. It's fully commented and
customisable for language, colours and date format.
The pop-up displays a month at a time from a specified
range of years. The optional year, month and day input
determines the initial month displayed. The year can be
in two or four digits while the month can be digits or a
month name abbreviation that can easily be set up for
non-English languages. This is ideal for combination
with server-side technologies to produce a professional
application.