Account for TZ offsets for event durations and next occurrence

lib/ice_cube/schedule.rb

@@ -456,7 +456,12 @@ def next_time(time, closing_time)
         end
         break unless min_time
         next (time = min_time + 1) if exception_time?(min_time)
-        break Occurrence.new(min_time, min_time + duration)
+
+        e_time = min_time + duration
+        # Make sure to add the timezone difference, in case we span tz zones (offsets)
+        # majority of cases this will be 0, but when we span tz zones, we need to account for it
+        e_time += TimeUtil.zone_offset_delta(min_time, e_time)
+        break Occurrence.new(min_time, e_time)
       end
     end
 

lib/ice_cube/time_util.rb

@@ -268,6 +268,17 @@ def self.subsec(time)
       end
     end
 
+    # Returns the timezone delta (seconds) between 2 times.
+    # - For times in the same timezone this will return 0.
+    # - For times than span offsets (think Daylight Savings time to Standard Time)
+    #   this number will be positive or negative, depening if you "spring foward" or "fall back".
+    # - The order of arguments is important, in 99% of use cases t0 is a date *before* t1 (aka time only moves foward).
+    # - For "fall back" this will be positive, aka we gained time (usually an hour, 3600)
+    # - For "spring foward" this will be negative, aka we lost time (usually an hour, -3600)
+    def self.zone_offset_delta(t0, t1)
+      t0.utc_offset - t1.utc_offset
+    end
+
     # A utility class for safely moving time around
     class TimeWrapper