[2019-02] Fix time zone transition out of DST (#15444)

monojenkins · marek-safar · commit e6f5369c2d24 · 2019-06-27T19:12:51.000+02:00
* Time zone DST out fix

* Add unit tests for Europe/Vatican, Iran and Europe/Guernsey time zones

* Disable the tests on WINAOT; fixed Iran time zone id
diff --git a/mcs/class/corlib/System/TimeZoneInfo.cs b/mcs/class/corlib/System/TimeZoneInfo.cs
@@ -1236,6 +1236,12 @@ private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset, out
 						isDst = true;
 					}
 
+					if (date >= new DateTime (tEnd.Ticks - current.DaylightDelta.Ticks, DateTimeKind.Utc))
+					{
+						offset = baseUtcOffset;
+						isDst = false;
+					}
+
 					return true;
 				}
 			}
diff --git a/mcs/class/corlib/Test/System/TimeZoneInfoTest.cs b/mcs/class/corlib/Test/System/TimeZoneInfoTest.cs
@@ -72,6 +72,10 @@ public static string MapTimeZoneId (string id)
 					return "W. Europe Standard Time";
 				case "Canada/Eastern":
 					return "Eastern Standard Time";
+				case "Asia/Tehran":
+					return "Iran Standard Time";
+				case "Europe/Guernsey":
+					return "GMT Standard Time";
 				default:
 					Assert.Fail ($"No mapping defined for zone id '{id}'");
 					return null;
@@ -459,6 +463,24 @@ public void Bug_9664 ()
 				date = new DateTime (2019, 3, 10, 3, 0, 0);
 				Assert.IsTrue (tzi.IsDaylightSavingTime (date));
 				Assert.AreEqual (new TimeSpan (-5, 0, 0), tzi.GetUtcOffset (date));
+
+#if !WINAOT // https://github.com/mono/mono/issues/15439
+				tzi = TimeZoneInfo.FindSystemTimeZoneById (MapTimeZoneId ("Europe/Vatican"));
+				date = new DateTime (2018, 10, 28, 2, 15, 0);
+				Assert.IsFalse (tzi.IsDaylightSavingTime (date));
+				Assert.AreEqual (new TimeSpan (1, 0, 0), tzi.GetUtcOffset (date));
+
+				tzi = TimeZoneInfo.FindSystemTimeZoneById (MapTimeZoneId ("Asia/Tehran"));
+				date = new DateTime (2018, 9, 21, 23, 15, 0);
+				Assert.IsFalse (tzi.IsDaylightSavingTime (date));
+				Assert.AreEqual (new TimeSpan (3, 30, 0), tzi.GetUtcOffset (date));
+
+				// for Greenwitch Mean Time (Guernsey)
+				tzi = TimeZoneInfo.FindSystemTimeZoneById (MapTimeZoneId ("Europe/Guernsey"));
+				date = new DateTime (2019, 10, 27, 1, 15, 0);
+				Assert.IsFalse (tzi.IsDaylightSavingTime (date));
+				Assert.AreEqual (new TimeSpan (0, 0, 0), tzi.GetUtcOffset (date));
+#endif
 			}
 		}
 

Original file line number	Diff line number	Diff line change
`@@ -1236,6 +1236,12 @@ private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset, out`
`1236`	`1236`	`isDst = true;`
`1237`	`1237`	`}`
`1238`	`1238`
	`1239`	`+ if (date >= new DateTime (tEnd.Ticks - current.DaylightDelta.Ticks, DateTimeKind.Utc))`
	`1240`	`+ {`
	`1241`	`+ offset = baseUtcOffset;`
	`1242`	`+ isDst = false;`
	`1243`	`+ }`
	`1244`	`+`
`1239`	`1245`	`return true;`
`1240`	`1246`	`}`
`1241`	`1247`	`}`