Time arithmetic accounts for Daylight Savings transition hour gain/loss

lib/chronic/repeaters/repeater_day_portion.rb

@@ -1,3 +1,5 @@
+require 'active_support/time'
+
 module Chronic
   class RepeaterDayPortion < Repeater #:nodoc:
     PORTIONS = {
@@ -31,23 +33,23 @@ def next(pointer)
         if now_seconds < @range.begin
           case pointer
           when :future
-            range_start = Chronic.construct(@now.year, @now.month, @now.day) + @range.begin
+            range_start = adjust_with_offset(@now, 0, @range)
           when :past
-            range_start = Chronic.construct(@now.year, @now.month, @now.day - 1) + @range.begin
+            range_start = adjust_with_offset(@now, -1, @range)
           end
         elsif now_seconds > @range.end
           case pointer
           when :future
-            range_start = Chronic.construct(@now.year, @now.month, @now.day + 1) + @range.begin
+            range_start = adjust_with_offset(@now, +1, @range)
           when :past
-            range_start = Chronic.construct(@now.year, @now.month, @now.day) + @range.begin
+            range_start = adjust_with_offset(@now, 0, @range)
           end
         else
           case pointer
           when :future
-            range_start = Chronic.construct(@now.year, @now.month, @now.day + 1) + @range.begin
+            range_start = adjust_with_offset(@now, +1, @range)
           when :past
-            range_start = Chronic.construct(@now.year, @now.month, @now.day - 1) + @range.begin
+            range_start = adjust_with_offset(@now, -1, @range)
           end
         end
         offset = (@range.end - @range.begin)
@@ -71,7 +73,7 @@ def next(pointer)
     def this(context = :future)
       super
 
-      range_start = Chronic.construct(@now.year, @now.month, @now.day) + @range.begin
+      range_start = adjust_with_offset(@now, 0, @range)
       range_end = construct_date_from_reference_and_offset(range_start)
       @current_span = Span.new(range_start, range_end)
     end
@@ -105,5 +107,13 @@ def construct_date_from_reference_and_offset(reference, offset = nil)
       hour_hand = (elapsed_seconds_for_range - minute_hand - second_hand) / (60 * 60) + reference.hour % 24
       Chronic.construct(reference.year, reference.month, reference.day, hour_hand, minute_hand, second_hand)
     end
+
+    # Uses Time#utc_offset to account for time gain/loss across Daylight Savings Time change boundaries
+    def adjust_with_offset(now, adjustment = 0, range)
+      initial = Chronic.construct(now.year, now.month, now.day) + adjustment.days
+      final = initial + range.begin
+
+      final + initial.utc_offset.seconds - final.utc_offset.seconds
+    end
   end
 end

test/test_parsing.rb

@@ -47,6 +47,14 @@ def test_handle_generic
     assert_equal Time.new(Time.now.year, Time.now.month, 28), time
   end
 
+  def test_handle_daylight_savings_transitions
+    time = parse_now("3/10/2019 12:35:04 PM")
+    assert_equal Time.local(2019, 3, 10, 12, 35, 04), time
+
+    time = parse_now("11/3/2019 11:35:04 PM")
+    assert_equal Time.local(2019, 11, 3, 23, 35, 04), time
+  end
+
   def test_handle_rmn_sd
     time = parse_now("aug 3")
     assert_equal Time.local(2007, 8, 3, 12), time

test/test_repeater_day_portion.rb

@@ -86,6 +86,19 @@ def test_pm_future_with_daylight_savings_time_boundary
 
     assert_equal Time.local(2012, 11, 4, 12), next_next_time.begin
     assert_equal Time.local(2012, 11, 4, 23, 59, 59), next_next_time.end
+
+    @now = Time.local(2012,11,3,12,40,12)
+    day_portion = Chronic::RepeaterDayPortion.new(:pm)
+    day_portion.start = @now
+
+    next_time = day_portion.next(:future)
+    assert_equal Time.local(2012, 11, 4, 12), next_time.begin
+    assert_equal Time.local(2012, 11, 4, 23, 59, 59), next_time.end
+
+    next_next_time = day_portion.next(:future)
+
+    assert_equal Time.local(2012, 11, 5, 12), next_next_time.begin
+    assert_equal Time.local(2012, 11, 5, 23, 59, 59), next_next_time.end
   end
 
   def test_morning_future