Brian McAllister coded an Unobtrusive Date-Picker that is accessible using the keyboard, that requires no embedded JS blocks and is suitable for use within documents served as application/xhtml+xml (as no document.write statements are used). The date-picker attempts to auto-detect the language of the users browser installation and download the corresponding language file from the server. It also has a nice fade-in/out effect. And finally, the script is available under a Creative Commons Attribution-ShareAlike 2.5 license, so it's free to use in both personal and professionnal projects.

Here's a quick feature list:

• Fully keyboard accessible
• Multiple date formats and date dividers supported
• Unobtrusive and nameSpace friendly
• Fully skinnable with CSS
• Both upper and lower date limits can be set
• Certain days of the week can be disabled
• Certain dates can be disabled/enabled
• Exclusions can be set using wildcards
• Includes "smart" localisation (16 languages currently available)
• Bespoke days of the week can be highlighted
• Works with single text inputs, split text inputs or select lists
• It’s free to use, even commercially

» Read the documentation
» See the demo
» Download the .zip archive