Jscalender module come with Jstools package in drupal 5 you can
download drupal jstools package from the drupal.org site.Jscalender
uses the jsCalendar javascript library, like using a special CSS class
called via #attribute in the form element array to convert textfields
into jcalendar enabled.



The jcalendar module uses hook_form_alter() to look for textfields with
the add-jcalendar class, I had to use something different than
jcalendar which is used later on the generated form elements by the
jQuery code.

Jquery is lightweight Java Script Library that provides functionality for may events in just few lines of code.To use jquery you must download first the jquery library file.

 You can download the latest version -- 1.2.6 the latest version from jquery site.

Functionality And Working Of Jquery :-

You should include a JavaScript file in your pages. There are many ways to include javascript in your page.
This has several advantages:

1. By updating one file, you update your script on all pages.
2. The pages themselves become slightly lighter, because the include file is cached by the browser, so it doesn't have to be reloaded every time the user loads a new page.

1. Including javascript file at top of page before body section inside head tag:-

"jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript.A lightweight framework that easily handles tedious DOM scripting chores."

Some quick feature of Jquery Are:-

* Lightweight Footprint
About 15KB in size (Minified and Gzipped).Very small size and so takes very little amount of time to load in memory.

* CSS3 Compliant
Supports CSS 1-3 and basic XPath syntax and rules.