Add joomla calendar from its library is pretty easy.

First of all, add this JHTML::_(’behavior.calendar’); code line in your class view (view.html.php) extends JView.

Then go to your form page include this:

<input type=”text” name=”start_date” id=”start_date” size=”20″ maxlength=”19″ value=”" />

<input type=”reset” value=”…” onclick=”return showCalendar(’start_date’,'%Y-%m-%d’);” />

Then it should be done.