signup form problem

[plugonline]

hello,

when i want to signup http://www.internetmarketingloont.nl...create_account to the store.
i've filled in all the fields and clickt on send.

then i get the next warning

fill in your date off birth like 22-05-1980

i have done this correctly but its was not accepted what do i have to do because noboby can signup for my shop now

i'm using version 1.3.8.

regards mervin