If a date input like date of birth is mandatory, in quick add brief form the calendar icon appears but clicking on it does nothing.
This is because quick add brief form creates a clone of inputs in the original form.
Note also that creating a clone of an input in another form does not update the form value in its DOM. It can generate errors.
In my opinion this feature should be reconsidered to hide unwanted fields instead of cloning wanted ones. Many bugs may be avoided.
Also date of birth has a small JS code showing age when date is changed.
How to reproduce this bug?
1. In the system preferences, add "dateofbirth" to "Patrons > General > BorrowerMandatoryField".
2. Go to the "Patrons" page.
3. Click "Quick add new patron" and select a patron category.
4. You will be shown the brief form.
5. Click on the calendar icon next to the "Date of birth" input field.
This is still valid - when marking dateofbirth mandatory, the datepicker doesn't work on the quick add patron form.
Yes, as well as all other date fields.
As Fridolin said we should rework the way the fields are displayed/hidden. It's not an easy fix.