issue-46477 Fix issue about checking last char in datetime string. (#46614)

* issue-46477 Fix issue about checking last char in datetime string.

* issue-46477 Fix comment: Add more tests with timezone part.

Author: lateapexearlyspeed

src/libraries/System.Private.CoreLib/src/System/Globalization/DateTimeParse.cs

@@ -3002,6 +3002,7 @@ private static bool ParseISO8601(ref DateTimeRawInfo raw, ref __DTString str, Da
                         result.SetBadDateTimeFailure();
                         return false;
                     }
+                    str.Index--;
                 }
                 else if (ch == 'Z' || ch == 'z')
                 {

src/libraries/System.Runtime/tests/System/DateTimeTests.cs

@@ -1041,6 +1041,18 @@ public static void Parse_InvalidArguments_Throws()
             Assert.Throws<FormatException>(() => DateTime.Parse(""));
             Assert.Throws<FormatException>(() => DateTime.Parse("", new MyFormatter()));
             Assert.Throws<FormatException>(() => DateTime.Parse("", new MyFormatter(), DateTimeStyles.NoCurrentDateDefault));
+
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000-07:00c"));
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000-07:00c", new MyFormatter()));
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000-07:00c", new MyFormatter(), DateTimeStyles.NoCurrentDateDefault));
+			
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000+00:00#"));
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000+00:00#", new MyFormatter()));
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000+00:00#", new MyFormatter(), DateTimeStyles.NoCurrentDateDefault));
+			
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000+00:00#\0"));
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000+00:00#\0", new MyFormatter()));
+            Assert.Throws<FormatException>(() => DateTime.Parse("2020-5-7T09:37:00.0000000+00:00#\0", new MyFormatter(), DateTimeStyles.NoCurrentDateDefault));
         }
 
         [Theory]
@@ -1711,6 +1723,11 @@ public static IEnumerable<object[]> Parse_ValidInput_Succeeds_MemberData()
             yield return new object[] { "2 2 2Z", CultureInfo.InvariantCulture, TimeZoneInfo.ConvertTimeFromUtc(new DateTime(2002, 2, 2, 0, 0, 0, DateTimeKind.Utc), TimeZoneInfo.Local) };
             yield return new object[] { "#10/10/2095#\0", CultureInfo.InvariantCulture, new DateTime(2095, 10, 10, 0, 0, 0) };
 
+            yield return new object[] { "2020-5-7T09:37:00.0000000+00:00\0", CultureInfo.InvariantCulture, TimeZoneInfo.ConvertTimeFromUtc(new DateTime(2020, 5, 7, 9, 37, 0, DateTimeKind.Utc), TimeZoneInfo.Local) };
+            yield return new object[] { "#2020-5-7T09:37:00.0000000+00:00#", CultureInfo.InvariantCulture, TimeZoneInfo.ConvertTimeFromUtc(new DateTime(2020, 5, 7, 9, 37, 0, DateTimeKind.Utc), TimeZoneInfo.Local) };
+            yield return new object[] { "#2020-5-7T09:37:00.0000000+00:00#\0", CultureInfo.InvariantCulture, TimeZoneInfo.ConvertTimeFromUtc(new DateTime(2020, 5, 7, 9, 37, 0, DateTimeKind.Utc), TimeZoneInfo.Local) };
+            yield return new object[] { "2020-5-7T09:37:00.0000000+00:00", CultureInfo.InvariantCulture, TimeZoneInfo.ConvertTimeFromUtc(new DateTime(2020, 5, 7, 9, 37, 0, DateTimeKind.Utc), TimeZoneInfo.Local) };
+
             if (PlatformDetection.IsNotInvariantGlobalization)
             {
                 DateTime today = DateTime.Today;