diff --git a/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs b/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs
index 5a6adf9415..3741ffa110 100644
--- a/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs
+++ b/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs
@@ -24,8 +24,9 @@ namespace Microsoft.Net.Http.Headers
             "d MMM yy H:m:s 'GMT'", // RFC 1123, no day-of-week, short year
             "d MMM yy H:m:s", // RFC 1123, no day-of-week, short year, no zone
 
-            "dddd, d'-'MMM'-'yy H:m:s 'GMT'", // RFC 850
+            "dddd, d'-'MMM'-'yy H:m:s 'GMT'", // RFC 850, short year
             "dddd, d'-'MMM'-'yy H:m:s", // RFC 850 no zone
+            "ddd, d'-'MMM'-'yyyy H:m:s 'GMT'", // RFC 850, long year
             "ddd MMM d H:m:s yyyy", // ANSI C's asctime() format
 
             "ddd, d MMM yyyy H:m:s zzz", // RFC 5322
diff --git a/test/Microsoft.Net.Http.Headers.Tests/DateParserTest.cs b/test/Microsoft.Net.Http.Headers.Tests/DateParserTest.cs
index 0fffc0c134..83fec06c46 100644
--- a/test/Microsoft.Net.Http.Headers.Tests/DateParserTest.cs
+++ b/test/Microsoft.Net.Http.Headers.Tests/DateParserTest.cs
@@ -2,29 +2,47 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using Xunit;
 
 namespace Microsoft.Net.Http.Headers
 {
     public class DateParserTest
     {
-        [Fact]
-        public void TryParse_SetOfValidValueStrings_ParsedCorrectly()
+        [Theory]
+        [MemberData(nameof(ValidStringData))]
+        public void TryParse_SetOfValidValueStrings_ParsedCorrectly(string input, DateTimeOffset expected)
         {
             // We don't need to validate all possible date values, since they're already tested in HttpRuleParserTest.
             // Just make sure the parser calls HttpRuleParser methods correctly.
-            CheckValidParsedValue("Tue, 15 Nov 1994 08:12:31 GMT", new DateTimeOffset(1994, 11, 15, 8, 12, 31, TimeSpan.Zero));
-            CheckValidParsedValue("      Sunday, 06-Nov-94 08:49:37 GMT   ", new DateTimeOffset(1994, 11, 6, 8, 49, 37, TimeSpan.Zero));
-            CheckValidParsedValue(" Tue,\r\n 15 Nov\r\n 1994 08:12:31 GMT   ", new DateTimeOffset(1994, 11, 15, 8, 12, 31, TimeSpan.Zero));
+            DateTimeOffset result;
+            Assert.True(HeaderUtilities.TryParseDate(input, out result));
+            Assert.Equal(expected, result);
         }
 
-        [Fact]
-        public void TryParse_SetOfInvalidValueStrings_ReturnsFalse()
+        private static IEnumerable<object[]> ValidStringData()
         {
-            CheckInvalidParsedValue(null);
-            CheckInvalidParsedValue(string.Empty);
-            CheckInvalidParsedValue("  ");
-            CheckInvalidParsedValue("!!Sunday, 06-Nov-94 08:49:37 GMT");
+            yield return new object[] { "Tue, 15 Nov 1994 08:12:31 GMT", new DateTimeOffset(1994, 11, 15, 8, 12, 31, TimeSpan.Zero) };
+            yield return new object[] { "      Sunday, 06-Nov-94 08:49:37 GMT   ", new DateTimeOffset(1994, 11, 6, 8, 49, 37, TimeSpan.Zero) };
+            yield return new object[] { " Tue,\r\n 15 Nov\r\n 1994 08:12:31 GMT   ", new DateTimeOffset(1994, 11, 15, 8, 12, 31, TimeSpan.Zero) };
+            yield return new object[] { "Sat, 09-Dec-2017 07:07:03 GMT ", new DateTimeOffset(2017, 12, 09, 7, 7, 3, TimeSpan.Zero) };
+        }
+
+        [Theory]
+        [MemberData(nameof(InvalidStringData))]
+        public void TryParse_SetOfInvalidValueStrings_ReturnsFalse(string input)
+        {
+            DateTimeOffset result;
+            Assert.False(HeaderUtilities.TryParseDate(input, out result));
+            Assert.Equal(new DateTimeOffset(), result);
+        }
+
+        private static IEnumerable<object[]> InvalidStringData()
+        {
+            yield return new object[] { null };
+            yield return new object[] { string.Empty };
+            yield return new object[] { "  " };
+            yield return new object[] { "!!Sunday, 06-Nov-94 08:49:37 GMT" };
         }
 
         [Fact]
@@ -36,23 +54,5 @@ namespace Microsoft.Net.Http.Headers
             Assert.Equal("Fri, 01 Jan 2010 01:01:01 GMT",
                 HeaderUtilities.FormatDate(new DateTimeOffset(2010, 1, 1, 1, 1, 1, TimeSpan.Zero)));
         }
-
-        #region Helper methods
-
-        private void CheckValidParsedValue(string input, DateTimeOffset expectedResult)
-        {
-            DateTimeOffset result;
-            Assert.True(HeaderUtilities.TryParseDate(input, out result));
-            Assert.Equal(expectedResult, result);
-        }
-
-        private void CheckInvalidParsedValue(string input)
-        {
-            DateTimeOffset result;
-            Assert.False(HeaderUtilities.TryParseDate(input, out result));
-            Assert.Equal(new DateTimeOffset(), result);
-        }
-
-        #endregion
     }
 }