Date Format for DHTML date / time selector

Our DHTML date calendar provides the date in the “dd/mmm/YY” format.
Is it possible to customize it to provide it in “dd/mmm/YYYY” format?

The speadsheet that is using it is not taking in the “dd/mmm/YY” format.
We want the calendar control itself to return the date in "dd/mmm/YYYY format.

How can this be achieved? Kindly suggest.