custom field date validation

i have 4 custom date fields for date-of-birth records in my membership database to cover children. i would like to validate that the date is correctly formatted as DD-MM-YYYY but if i use the function validate[custom[date],past[now]] this does confirm that an entered date is correctly formatted but does not allow for the field to be blank.
The date fields are not mandatory.

is there a way to set the function so that IF a date is entered it is validated but that no entry at all is also allowed?

Thank you.

Hello Mike

Honestly, this is controlled by the validation library which we are using, so I am afraid of we could not make the change

Maybe you can submit a support ticket sending us super admin account of your site and link to the page? We will try to look at it to see if we can come up with a solution for that problem

Regards,

Tuan