Always write both DAYLIGHT and STANDARD periods to VTIMEZONE blocks.

lib/ri_cal/component/t_z_info_timezone.rb

@@ -66,13 +66,21 @@ def export_to(export_stream)
   class Periods #:nodoc: all
 
     def initialize
-      @dst_period = @std_period = @previous_period = nil
+      @daylight_period = @standard_period = @previous_period = nil
     end
 
     def empty?
       @periods.nil? || @periods.empty?
     end
 
+    def has_standard?
+      !@standard_period.nil?
+    end
+
+    def has_daylight?
+      !@daylight_period.nil?
+    end
+
     def daylight_period(this_period, previous_period)
       @daylight_period ||= Period.new("DAYLIGHT", this_period, previous_period)
     end
@@ -142,10 +150,14 @@ def export_utc_to(export_stream, utc_start, utc_end) #:nodoc:
      #start with the period before the one containing utc_start
     prev_period = period.utc_start && tzinfo_timezone.period_for_utc(period.utc_start - 1)
     period = prev_period if prev_period
-    while period && period.utc_start && period.utc_start < utc_end
+    while period && period.utc_start && period.utc_start <= utc_end
       periods.add_period(period)
+      prev_period = period
       period = period.utc_end && tzinfo_timezone.period_for_utc(period.utc_end + 1)
     end
+    if period && prev_period && period.dst? != prev_period.dst? && !(periods.has_daylight? && periods.has_standard?)
+      periods.add_period(period)
+    end
     periods.add_period(initial_period, :force) if periods.empty?
     periods.export_to(export_stream)
     export_stream.puts "END:VTIMEZONE\n"

spec/ri_cal/component/t_z_info_timezone_spec.rb

@@ -36,6 +36,62 @@
 ENDDATA
   end
 
+  it "should produce an rfc representation that Outlook will not barf on" do
+    tz = RiCal::Component::TZInfoTimezone.new(TZInfo::Timezone.get("America/New_York"))
+    local_first = DateTime.parse("Apr 10, 2007")
+    local_last = DateTime.parse("Apr 16, 2007")
+    utc_first = tz.local_to_utc(local_first)
+    utc_last = tz.local_to_utc(local_last)
+    rez = tz.to_rfc2445_string(utc_first, utc_last)
+    rez.should == <<-ENDDATA
+BEGIN:VTIMEZONE
+TZID;X-RICAL-TZSOURCE=TZINFO:America/New_York
+BEGIN:DAYLIGHT
+DTSTART:20070311T020000
+RDATE:20070311T020000
+TZOFFSETFROM:-0500
+TZOFFSETTO:-0400
+TZNAME:EDT
+END:DAYLIGHT
+BEGIN:STANDARD
+DTSTART:20071104T020000
+RDATE:20071104T020000
+TZOFFSETFROM:-0400
+TZOFFSETTO:-0500
+TZNAME:EST
+END:STANDARD
+END:VTIMEZONE
+ENDDATA
+  end
+
+  it "should produce an rfc representation that Outlook will not barf on at DST switch" do
+    tz = RiCal::Component::TZInfoTimezone.new(TZInfo::Timezone.get("America/New_York"))
+    local_first = DateTime.parse("Mar 11, 2007 03:00:00 AM")
+    local_last = DateTime.parse("Mar 11, 2007 03:00:00 AM")
+    utc_first = tz.local_to_utc(local_first)
+    utc_last = tz.local_to_utc(local_last)
+    rez = tz.to_rfc2445_string(utc_first, utc_last)
+    rez.should == <<-ENDDATA
+BEGIN:VTIMEZONE
+TZID;X-RICAL-TZSOURCE=TZINFO:America/New_York
+BEGIN:DAYLIGHT
+DTSTART:20070311T020000
+RDATE:20070311T020000
+TZOFFSETFROM:-0500
+TZOFFSETTO:-0400
+TZNAME:EDT
+END:DAYLIGHT
+BEGIN:STANDARD
+DTSTART:20071104T020000
+RDATE:20071104T020000
+TZOFFSETFROM:-0400
+TZOFFSETTO:-0500
+TZNAME:EST
+END:STANDARD
+END:VTIMEZONE
+ENDDATA
+  end
+
   TZInfo::Timezone.all_identifiers.each do |tz|
     context "TZInfo timezone #{tz}" do
       before(:each) do

spec/spec_helper.rb

@@ -4,6 +4,7 @@
 require 'cgi'
 require 'tzinfo'
 
+alias :context :describe
 
 module Kernel
   if ENV.keys.find {|env_var| env_var.match(/^TM_/)}