Date field of Contact form 7 is not working

[ Moderator note: moved to Fixing WordPress. ]

I’m using contact form 7 plugin in WordPress, and my form has date field. Whenever I submit form it shows error as: “The date format is incorrect.”

<div class="datepicker-input" data-date-format="mm/dd/yy" data-first-day="0"> [date* your-date min:2017-01-01 max:2017-12-31 date-format:mm/dd/yy id:reservation-date step:7 name:date class:required " Pick Your Day"] 
</div>

I’ve also inserted this code on mail section. But it didn’t work.
Date: [_format_your-date "D, d M y"]