Is their any JavaScript Calendar control which can handle the different Date Time Formats easily?
BasicDatePicker is the best one I've come across. We use it at the moment, and our users love it. Well worth $100.
DatePicker is a JQuery plug-in that we've found very useful.
From the docs:
You can restrict the functionality in various ways, you can select date ranges, and you can provide the date in picker in a number of languages.
There's also a full section on localisation which can be handily used to show the picker defaulting to your user's local date/time format by setting a single param, e.g.
dateFormat: 'mm/dd/yy'
I like the Calendar in the AJAX Control Toolkit (http://www.codeplex.com/AjaxControlToolkit) but it's obviously only useful when you are using ASP.NET.
For pure JavaScript I like the DatePicker for jQuery
The YUI Calendar is a nice one, however if you don't want to pull the whole YUI framework in, you might like the JS calendar from Dynarch. It is extreemly customizable and served me well in several projects.
If you're on APS.NET you could use Ra-Ajax Calendar which can easily be localized to everything ASP.NET and the .Net Framework can handle...
Here is another one for you very easy to use with so many customization options.
dijit.Calendar and the corresponding dijit.form.DateTextBox has built-in localization for dozens of languages. Based on the locale presented by the developer, it will choose the right conventions. There are several skins available, or you can create your own custom template.
The best one I found is the Jeremy Songma's calendar. It is based on Prototype, and required a few customizations for my project. I chose it for its well written code too.