- Added datetime with milliseconds format to StringExtensions

- Added DateTimeResponse class to Test/SampleClasses/misc.cs
- Added test for fix

RestSharp.Tests/JsonTests.cs

@@ -845,6 +845,18 @@ public void Can_Deserialize_Dictionary_with_Null()
             Assert.IsNull(dictionary["Null"]);
         }
 
+        [Test]
+        public void Can_Deserialize_Date_With_Milliseconds()
+        {
+            const string content = "{ \"CreatedOn\": \"2018-10-01T14:39:00.234Z\" }";
+            JsonDeserializer json = new JsonDeserializer();
+            DateTimeResponse output = json.Deserialize<DateTimeResponse>(new RestResponse { Content = content });
+            DateTime expected = DateTime.Parse("2018-10-01 14:39:00.234", CultureInfo.InvariantCulture);
+
+            Assert.NotNull(output);
+            Assert.AreEqual(expected.ToString(), output.CreatedOn.ToString());
+        }
+
         private static string CreateJsonWithUnderscores()
         {
             JsonObject doc = new JsonObject();

RestSharp.Tests/SampleClasses/misc.cs

@@ -333,4 +333,9 @@ public class WrongNote
         [DeserializeAs(Content = true)]
         public string Text { get; set; }
     }
+
+    public class DateTimeResponse
+    {
+        public DateTime CreatedOn { get; set; }
+    }
 }

RestSharp/Extensions/StringExtensions.cs

@@ -143,13 +143,14 @@ private static DateTime ParseFormattedDate(string input, CultureInfo culture)
                 "yyyy-MM-dd HH:mm:ssZ",
                 "yyyy-MM-ddTHH:mm:ss",
                 "yyyy-MM-ddTHH:mm:sszzzzzz",
+                "yyyy-MM-ddTHH:mm:ss.fffZ",
                 "M/d/yyyy h:mm:ss tt" // default format for invariant culture
             };
 
             if (DateTime.TryParseExact(input, formats, culture,
                 DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var date))
                 return date;
-
+            
             return DateTime.TryParse(input, culture, DateTimeStyles.None, out date) ? date : default(DateTime);
         }