text_field with type :date doesn't get bound

This date field:

<%= f.text_field :my_date, id: 'id-123', type: 'date' %>

doesn't get bound to the value of my_date of the model on the, for example, edit page. When I load the page, it's always "empty".

Why is that? I also tried:

<%= f.text_field :my_date, id: 'id-123', type: 'date', value: '11/11/11' %>
<%= f.text_field :my_date, id: 'id-123', type: 'date', value: '11-11-11' %>

and it also didn't work.