diff --git a/src/Nest/DSL/Query/RangeQueryDescriptor.cs b/src/Nest/DSL/Query/RangeQueryDescriptor.cs
index 5371121a859..d1f2f90bd2c 100644
--- a/src/Nest/DSL/Query/RangeQueryDescriptor.cs
+++ b/src/Nest/DSL/Query/RangeQueryDescriptor.cs
@@ -188,25 +188,25 @@ public RangeQueryDescriptor<T> LowerOrEquals(string to)
 
 		public RangeQueryDescriptor<T> Greater(DateTime? from, string format = "yyyy-MM-dd'T'HH:mm:ss.fff")
 		{
-			this.Self.GreaterThan = from.HasValue ? from.Value.ToString(format) : null;
+			this.Self.GreaterThan = from.HasValue ? from.Value.ToString(format, CultureInfo.InvariantCulture) : null;
 			return this;
 		}
 
 		public RangeQueryDescriptor<T> GreaterOrEquals(DateTime? from, string format = "yyyy-MM-dd'T'HH:mm:ss.fff")
 		{
-			this.Self.GreaterThanOrEqualTo = from.HasValue ? from.Value.ToString(format) : null;
+			this.Self.GreaterThanOrEqualTo = from.HasValue ? from.Value.ToString(format, CultureInfo.InvariantCulture) : null;
 			return this;
 		}
 
 		public RangeQueryDescriptor<T> Lower(DateTime? to, string format = "yyyy-MM-dd'T'HH:mm:ss.fff")
 		{
-			this.Self.LowerThan = to.HasValue ? to.Value.ToString(format) : null;
+			this.Self.LowerThan = to.HasValue ? to.Value.ToString(format, CultureInfo.InvariantCulture) : null;
 			return this;
 		}
 
 		public RangeQueryDescriptor<T> LowerOrEquals(DateTime? to, string format = "yyyy-MM-dd'T'HH:mm:ss.fff")
 		{
-			this.Self.LowerThanOrEqualTo = to.HasValue ? to.Value.ToString(format) : null;
+			this.Self.LowerThanOrEqualTo = to.HasValue ? to.Value.ToString(format, CultureInfo.InvariantCulture) : null;
 			return this;
 		}
 
diff --git a/src/Nest/Resolvers/ElasticContractResolver.cs b/src/Nest/Resolvers/ElasticContractResolver.cs
index 9c7f09e5b5c..ead36a41bd7 100644
--- a/src/Nest/Resolvers/ElasticContractResolver.cs
+++ b/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 --git a/src/Tests/Nest.Tests.Unit/Internals/Serialize/SerializeTests.cs b/src/Tests/Nest.Tests.Unit/Internals/Serialize/SerializeTests.cs
index 0bc743a5fa8..a1a981b4a50 100644
--- a/src/Tests/Nest.Tests.Unit/Internals/Serialize/SerializeTests.cs
+++ b/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()
 		{
diff --git a/src/Tests/Nest.Tests.Unit/Nest.Tests.Unit.csproj b/src/Tests/Nest.Tests.Unit/Nest.Tests.Unit.csproj
index e2073bc986f..3d82e334ba5 100644
--- a/src/Tests/Nest.Tests.Unit/Nest.Tests.Unit.csproj
+++ b/src/Tests/Nest.Tests.Unit/Nest.Tests.Unit.csproj
@@ -416,6 +416,7 @@
     <Compile Include="Reproduce\Reproduce1396Tests.cs" />
     <Compile Include="Reproduce\Reproduce1199Tests.cs" />
     <Compile Include="Reproduce\Reproduce1146Tests.cs" />
+    <Compile Include="Reproduce\Reproduce1440Tests.cs" />
     <Compile Include="Reproduce\Reproduce1464Tests.cs" />
     <Compile Include="Reproduce\Reproduce629Tests.cs" />
     <Compile Include="Reproduce\Reproduce1187Tests.cs" />