The first thing that I must address, YUI is actually a client end calendar control that puts everything using javascript.
ASP.NET is actually a server side technology which ensures how the page is produced to the client.
ASP.NET supports globalization using Resource files. So prepare a resource file in your server, and whenever you parse the javascript, just place server tags <% %> to replace the localized strings with particular text you want.
No one built specific to YUI control as it is basically very specific to your work. Please take a look into :
http://www.codeproject.com/KB/aspnet/LocalizationPackage.asp[
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And find out how it replaces text with appropriate resource keys.
Next take a look into :
http://developer.yahoo.com/yui/examples/calendar/germany.htm[
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You can see YUI supports you to change text in calendar. You can specify MONTHS_LONG, WEEKDAYS_LONG using setProperty. Once you change the text from server side, the calendar will show this automatically.
I hope you could create this yourself.
Cheers. :thumbsup: