fix #1227 force all dates to be serialized with InvariantCulture

Author: Mpdreamz

Diff for: src/Nest/Resolvers/ElasticContractResolver.cs

@@ -7,6 +7,7 @@
 using System.Linq;
 using System.Reflection;
 using System.Collections;
+using System.Globalization;
 using Nest.Resolvers.Converters;
 
 namespace Nest.Resolvers
@@ -52,7 +53,7 @@ protected override JsonContract CreateContract(Type objectType)
 				contract.Converter = new AggregationConverter();
 
 			else if (objectType == typeof(DateTime) || objectType == typeof(DateTime?))
-				contract.Converter = new IsoDateTimeConverter();
+				contract.Converter = new IsoDateTimeConverter() { Culture = CultureInfo.InvariantCulture };
 
 			else if (typeof(IHit<object>).IsAssignableFrom(objectType))
 				contract.Converter = new DefaultHitConverter();

Diff for: src/Tests/Nest.Tests.Unit/Internals/Serialize/SerializeTests.cs

@@ -1,9 +1,13 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Globalization;
 using System.Reflection;
+using System.Threading;
 using NUnit.Framework;
 using Nest.Tests.MockData.Domain;
 using Elasticsearch.Net;
+using FluentAssertions;
 
 namespace Nest.Tests.Unit.Internals.Serialize
 {
@@ -48,6 +52,24 @@ public void ClassWithCollectionSerializes()
 			this.JsonEquals(json, MethodInfo.GetCurrentMethod());
 		}
 
+		[Test]
+		public void DateTimeIgnoresCurrentCulture()
+		{
+			var t = new Thread(() =>
+			{
+				var cultureInfo = new CultureInfo("IT-it");
+				cultureInfo.DateTimeFormat.DateSeparator = ".";
+				cultureInfo.DateTimeFormat.TimeSeparator = ".";
+				Thread.CurrentThread.CurrentCulture = cultureInfo;
+				Thread.CurrentThread.CurrentUICulture = cultureInfo;
+
+				var serialized = _client.Serializer.Serialize(new DateTime(2015, 01, 30, 08, 52, 32, 443)).Utf8String();
+				serialized.Should().EndWith(":32.443\"");
+			});
+			t.Start();
+			t.Join(TimeSpan.FromSeconds(5));
+		}
+
 		[Test]
 		public void SerializingSearchIsFastEnough()
 		{