Contact Form 7 Datepicker by shockware is a WordPress plugin based on jsDatePick script..
The plugin implements a new [date] tag in Contact Form 7 that adds a date field to a form. When clicking the field a calendar pops up enabling your site visitors to easily select any date. To use, just insert the [date your-field-name] or [date* your-required-field-name] to any form in Contact Form 7 edit area where you want users to input a date.
Download and info: http://wordpress.org/extend/plugins/contact-form-7-datepicker/