How to style timezone_menu()

Hard to know without seeing your timezone_menu() code. Like is it outputting HTML, using the form_dropdown() helper, or what?

But using CI's native form_dropdown(), it would be (just like the docs state) entering the custom id/class/other attributes in the 4th parameter.

Code:

echo form_dropdown('name_of_dropdown', $dropdown_value_array, $selected_value, 'id="my-id" class="some-class"');