ActionView::Helpers::InstanceTag#to_date_tag help

I’m trying to read through the code, hoping to find a way to custom
style select boxes for a date_select and can’t figure out this code.
Any help appreciated:

def to_date_tag() defaults = DEFAULT_DATE_OPTIONS.dup date = value(object) || options = { |position| defaults.merge(:prefix => "#{@object_name}[#{@method_name}(#{position}i)]") } html_day_select(date, + html_month_select(date, + html_year_select(date, end

Specifically, where are html_day_select, html_month_select, and
html_year_select defined? Is there a method_missing definition that I’m
not finding that’s handling these calls?