diff --git a/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs b/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs
index 46aa08c8..9d9789ba 100644
--- a/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs
+++ b/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs
@@ -151,6 +151,26 @@ namespace Newtonsoft.Json.Tests.Converters
             return sw.ToString();
         }
 
+#if !PORTABLE || NETSTANDARD1_3 || NETSTANDARD2_0
+        [Test]
+        public void DeserializeXmlNode_DefaultDate()
+        {
+            XmlDocument xmlNode = JsonConvert.DeserializeXmlNode("{Time: \"0001-01-01T00:00:00\"}");
+
+            Assert.AreEqual("<Time>0001-01-01T00:00:00</Time>", xmlNode.OuterXml);
+        }
+#endif
+
+#if !NET20
+        [Test]
+        public void DeserializeXNode_DefaultDate()
+        {
+            var xmlNode = JsonConvert.DeserializeXNode("{Time: \"0001-01-01T00:00:00\"}");
+
+            Assert.AreEqual("<Time>0001-01-01T00:00:00</Time>", xmlNode.ToString());
+        }
+#endif
+
         [Test]
         public void WriteJsonNull()
         {
diff --git a/Src/Newtonsoft.Json/Converters/BinaryConverter.cs b/Src/Newtonsoft.Json/Converters/BinaryConverter.cs
index 97e20d8d..83f0717b 100644
--- a/Src/Newtonsoft.Json/Converters/BinaryConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/BinaryConverter.cs
@@ -74,9 +74,9 @@ namespace Newtonsoft.Json.Converters
             }
 #endif
 #if HAVE_ADO_NET
-            if (value is SqlBinary)
+            if (value is SqlBinary binary)
             {
-                return ((SqlBinary)value).Value;
+                return binary.Value;
             }
 #endif
 
diff --git a/Src/Newtonsoft.Json/Converters/BsonObjectIdConverter.cs b/Src/Newtonsoft.Json/Converters/BsonObjectIdConverter.cs
index 533e113d..5571c37f 100644
--- a/Src/Newtonsoft.Json/Converters/BsonObjectIdConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/BsonObjectIdConverter.cs
@@ -46,8 +46,7 @@ namespace Newtonsoft.Json.Converters
         {
             BsonObjectId objectId = (BsonObjectId)value;
 
-            BsonWriter bsonWriter = writer as BsonWriter;
-            if (bsonWriter != null)
+            if (writer is BsonWriter bsonWriter)
             {
                 bsonWriter.WriteObjectId(objectId.Value);
             }
diff --git a/Src/Newtonsoft.Json/Converters/DataTableConverter.cs b/Src/Newtonsoft.Json/Converters/DataTableConverter.cs
index ffb7af01..794a0f29 100644
--- a/Src/Newtonsoft.Json/Converters/DataTableConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/DataTableConverter.cs
@@ -94,9 +94,7 @@ namespace Newtonsoft.Json.Converters
                 return null;
             }
 
-            DataTable dt = existingValue as DataTable;
-
-            if (dt == null)
+            if (!(existingValue is DataTable dt))
             {
                 // handle typed datasets
                 dt = (objectType == typeof(DataTable))
diff --git a/Src/Newtonsoft.Json/Converters/EntityKeyMemberConverter.cs b/Src/Newtonsoft.Json/Converters/EntityKeyMemberConverter.cs
index 89f9c257..aeeb87a0 100644
--- a/Src/Newtonsoft.Json/Converters/EntityKeyMemberConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/EntityKeyMemberConverter.cs
@@ -71,8 +71,7 @@ namespace Newtonsoft.Json.Converters
 
             if (keyValueType != null)
             {
-                string valueJson;
-                if (JsonSerializerInternalWriter.TryConvertToString(keyValue, keyValueType, out valueJson))
+                if (JsonSerializerInternalWriter.TryConvertToString(keyValue, keyValueType, out string valueJson))
                 {
                     writer.WriteValue(valueJson);
                 }
diff --git a/Src/Newtonsoft.Json/Converters/IsoDateTimeConverter.cs b/Src/Newtonsoft.Json/Converters/IsoDateTimeConverter.cs
index 312a8595..7f058df8 100644
--- a/Src/Newtonsoft.Json/Converters/IsoDateTimeConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/IsoDateTimeConverter.cs
@@ -80,10 +80,8 @@ namespace Newtonsoft.Json.Converters
         {
             string text;
 
-            if (value is DateTime)
+            if (value is DateTime dateTime)
             {
-                DateTime dateTime = (DateTime)value;
-
                 if ((_dateTimeStyles & DateTimeStyles.AdjustToUniversal) == DateTimeStyles.AdjustToUniversal
                     || (_dateTimeStyles & DateTimeStyles.AssumeUniversal) == DateTimeStyles.AssumeUniversal)
                 {
@@ -93,9 +91,8 @@ namespace Newtonsoft.Json.Converters
                 text = dateTime.ToString(_dateTimeFormat ?? DefaultDateTimeFormat, Culture);
             }
 #if HAVE_DATE_TIME_OFFSET
-            else if (value is DateTimeOffset)
+            else if (value is DateTimeOffset dateTimeOffset)
             {
-                DateTimeOffset dateTimeOffset = (DateTimeOffset)value;
                 if ((_dateTimeStyles & DateTimeStyles.AdjustToUniversal) == DateTimeStyles.AdjustToUniversal
                     || (_dateTimeStyles & DateTimeStyles.AssumeUniversal) == DateTimeStyles.AssumeUniversal)
                 {
@@ -149,9 +146,9 @@ namespace Newtonsoft.Json.Converters
                 }
 
                 // converter is expected to return a DateTime
-                if (reader.Value is DateTimeOffset)
+                if (reader.Value is DateTimeOffset offset)
                 {
-                    return ((DateTimeOffset)reader.Value).DateTime;
+                    return offset.DateTime;
                 }
 #endif
 
diff --git a/Src/Newtonsoft.Json/Converters/JavaScriptDateTimeConverter.cs b/Src/Newtonsoft.Json/Converters/JavaScriptDateTimeConverter.cs
index 40b18dee..146c3ea5 100644
--- a/Src/Newtonsoft.Json/Converters/JavaScriptDateTimeConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/JavaScriptDateTimeConverter.cs
@@ -44,16 +44,14 @@ namespace Newtonsoft.Json.Converters
         {
             long ticks;
 
-            if (value is DateTime)
+            if (value is DateTime dateTime)
             {
-                DateTime dateTime = (DateTime)value;
                 DateTime utcDateTime = dateTime.ToUniversalTime();
                 ticks = DateTimeUtils.ConvertDateTimeToJavaScriptTicks(utcDateTime);
             }
 #if HAVE_DATE_TIME_OFFSET
-            else if (value is DateTimeOffset)
+            else if (value is DateTimeOffset dateTimeOffset)
             {
-                DateTimeOffset dateTimeOffset = (DateTimeOffset)value;
                 DateTimeOffset utcDateTimeOffset = dateTimeOffset.ToUniversalTime();
                 ticks = DateTimeUtils.ConvertDateTimeToJavaScriptTicks(utcDateTimeOffset.UtcDateTime);
             }
diff --git a/Src/Newtonsoft.Json/Converters/RegexConverter.cs b/Src/Newtonsoft.Json/Converters/RegexConverter.cs
index c63e6cce..8dd20243 100644
--- a/Src/Newtonsoft.Json/Converters/RegexConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/RegexConverter.cs
@@ -57,8 +57,7 @@ namespace Newtonsoft.Json.Converters
             Regex regex = (Regex)value;
 
 #pragma warning disable 618
-            BsonWriter bsonWriter = writer as BsonWriter;
-            if (bsonWriter != null)
+            if (writer is BsonWriter bsonWriter)
             {
                 WriteBson(bsonWriter, regex);
             }
diff --git a/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs b/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs
index 63f0a03c..4dd4f4b7 100644
--- a/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs
@@ -1867,40 +1867,44 @@ namespace Newtonsoft.Json.Converters
                     return reader.Value?.ToString();
                 case JsonToken.Integer:
 #if HAVE_BIG_INTEGER
-                    if (reader.Value is BigInteger)
+                    if (reader.Value is BigInteger i)
                     {
-                        return ((BigInteger)reader.Value).ToString(CultureInfo.InvariantCulture);
+                        return i.ToString(CultureInfo.InvariantCulture);
                     }
 #endif
                     return XmlConvert.ToString(Convert.ToInt64(reader.Value, CultureInfo.InvariantCulture));
                 case JsonToken.Float:
-                    if (reader.Value is decimal)
+                {
+                    if (reader.Value is decimal d)
                     {
-                        return XmlConvert.ToString((decimal)reader.Value);
+                        return XmlConvert.ToString(d);
                     }
 
-                    if (reader.Value is float)
+                    if (reader.Value is float f)
                     {
-                        return XmlConvert.ToString((float)reader.Value);
+                        return XmlConvert.ToString(f);
                     }
 
                     return XmlConvert.ToString(Convert.ToDouble(reader.Value, CultureInfo.InvariantCulture));
+                }
                 case JsonToken.Boolean:
                     return XmlConvert.ToString(Convert.ToBoolean(reader.Value, CultureInfo.InvariantCulture));
                 case JsonToken.Date:
+                {
 #if HAVE_DATE_TIME_OFFSET
-                    if (reader.Value is DateTimeOffset)
+                    if (reader.Value is DateTimeOffset offset)
                     {
-                        return XmlConvert.ToString((DateTimeOffset)reader.Value);
+                        return XmlConvert.ToString(offset);
                     }
 
 #endif
                     DateTime d = Convert.ToDateTime(reader.Value, CultureInfo.InvariantCulture);
-#if !PORTABLE
+#if !PORTABLE || NETSTANDARD1_3
                     return XmlConvert.ToString(d, DateTimeUtils.ToSerializationMode(d.Kind));
 #else
-                    return XmlConvert.ToString(d, DateTimeUtils.ToDateTimeFormat(d.Kind));
+                    return d.ToString(DateTimeUtils.ToDateTimeFormat(d.Kind), CultureInfo.InvariantCulture);
 #endif
+                }
                 case JsonToken.Bytes:
                     return Convert.ToBase64String((byte[])reader.Value);
                 case JsonToken.Null:
@@ -1934,8 +1938,7 @@ namespace Newtonsoft.Json.Converters
             {
                 foreach (IXmlNode childNode in nestedArrayElement.ChildNodes)
                 {
-                    IXmlElement element = childNode as IXmlElement;
-                    if (element != null && element.LocalName == propertyName)
+                    if (childNode is IXmlElement element && element.LocalName == propertyName)
                     {
                         AddJsonArrayAttribute(element, document);
                         break;
@@ -2005,8 +2008,7 @@ namespace Newtonsoft.Json.Converters
                                     attributeValue = ConvertTokenToXmlValue(reader);
                                     attributeNameValues.Add(attributeName, attributeValue);
 
-                                    string namespacePrefix;
-                                    if (IsNamespaceAttribute(attributeName, out namespacePrefix))
+                                    if (IsNamespaceAttribute(attributeName, out string namespacePrefix))
                                     {
                                         manager.AddNamespace(namespacePrefix, attributeValue);
                                     }
@@ -2205,8 +2207,7 @@ namespace Newtonsoft.Json.Converters
                             {
                                 foreach (IXmlNode childNode in currentNode.ChildNodes)
                                 {
-                                    IXmlElement element = childNode as IXmlElement;
-                                    if (element != null && element.LocalName == propertyName)
+                                    if (childNode is IXmlElement element && element.LocalName == propertyName)
                                     {
                                         AddJsonArrayAttribute(element, document);
                                         break;
diff --git a/Src/Newtonsoft.Json/Utilities/DateTimeUtils.cs b/Src/Newtonsoft.Json/Utilities/DateTimeUtils.cs
index 807c3a1a..19e6ce30 100644
--- a/Src/Newtonsoft.Json/Utilities/DateTimeUtils.cs
+++ b/Src/Newtonsoft.Json/Utilities/DateTimeUtils.cs
@@ -58,7 +58,7 @@ namespace Newtonsoft.Json.Utilities
 #endif
         }
 
-#if !(PORTABLE40 || PORTABLE)
+#if !(PORTABLE40 || PORTABLE) || NETSTANDARD1_3
         public static XmlDateTimeSerializationMode ToSerializationMode(DateTimeKind kind)
         {
             switch (kind)