span> <span class="identifier">date_type</span><span class="special">::</span><span class="identifier">year_type</span>                            <a name="boost.date_time.us_dst_rules.year_type"></a><span class="identifier">year_type</span><span class="special">;</span>         
  <span class="keyword">typedef</span> <span class="identifier">date_type</span><span class="special">::</span><span class="identifier">calendar_type</span>                        <a name="boost.date_time.us_dst_rules.calendar_type