Why is the "Date" field not showing on the emailed form submission pdf attachment?

Why is the "Date" field not showing on the pdf attached to the submission email notification?

Hello,

We're sorry for the inconvenience.

I've just cloned your "Membership Details" form to see the problem. However everything seems the way it should be. Here is a screenshot from a submission notification email pdf attachment: 

As you can see date (and all the other fields) filled properly. Which submission are you experiencing this problem? And can you tell us which date field has this problem?