This is how it should look on all the browsers:
And this is how it looks on Safari, for example:
This is the code that I am using at the moment:
<%= date_field 'birth_date', rel => 'birth_date',
class => "form-control", required => undef %>
You're using the Mojolicious date_field
tag helper. This generates a <input type="date">
HTML input field.
But support for the date input isn't universal. In particular, you'll see that Safari doesn't support it.
So you'll need to use some kind of plugin, I guess. If you're using jQuery, then one of these might work for you.