[Brian]

My understanding (I'm not a developer, so I may be wrong) is that we're using a standard Mac OS X control there.

Microsoft have likely implemented their own version of a date picker - that has some advantages, but also means that we're spending time producing our own version of the tools that Apple gives us, rather than adding features to our own code.

If Apple improves the standard control in future versions of the OS, we have to yank out our own version of the control, and in the meantime, we have more code to maintain. What you're requesting is possible, but there are tradeoffs involved.