Finalized date time handling

src/Squidex.Infrastructure.MongoDb/MongoDb/BsonJsonConverter.cs

@@ -6,6 +6,7 @@
 // ==========================================================================
 
 using System;
+using System.Globalization;
 using MongoDB.Bson;
 using Newtonsoft.Json.Linq;
 
@@ -95,11 +96,18 @@ namespace Squidex.Infrastructure.MongoDb
 
                         if (value is DateTime dateTime)
                         {
-                            return dateTime.ToString("yyyy-MM-ddTHH:mm:ssK");
+                            return dateTime.ToString("yyyy-MM-ddTHH:mm:ssK", CultureInfo.InvariantCulture);
                         }
                         else if (value is DateTimeOffset dateTimeOffset)
                         {
-                            return dateTimeOffset.UtcDateTime.ToString("yyyy-MM-ddTHH:mm:ssK");
+                            if (dateTimeOffset.Offset == TimeSpan.Zero)
+                            {
+                                return dateTimeOffset.UtcDateTime.ToString("yyyy-MM-ddTHH:mm:ssK", CultureInfo.InvariantCulture);
+                            }
+                            else
+                            {
+                                return dateTimeOffset.ToString("yyyy-MM-ddTHH:mm:ssK", CultureInfo.InvariantCulture);
+                            }
                         }
                         else
                         {

src/Squidex.Infrastructure.MongoDb/MongoDb/BsonJsonWriter.cs

@@ -135,12 +135,19 @@ namespace Squidex.Infrastructure.MongoDb
 
         public override void WriteValue(DateTime value)
         {
-            bsonWriter.WriteString(value.ToString("yyyy-MM-ddTHH:mm:ssZ", CultureInfo.InvariantCulture));
+            bsonWriter.WriteString(value.ToString("yyyy-MM-ddTHH:mm:ssK", CultureInfo.InvariantCulture));
         }
 
         public override void WriteValue(DateTimeOffset value)
         {
-            bsonWriter.WriteString(value.ToString("yyyy-MM-ddTHH:mm:ssZ", CultureInfo.InvariantCulture));
+            if (value.Offset == TimeSpan.Zero)
+            {
+                bsonWriter.WriteString(value.UtcDateTime.ToString("yyyy-MM-ddTHH:mm:ssK", CultureInfo.InvariantCulture));
+            }
+            else
+            {
+                bsonWriter.WriteString(value.UtcDateTime.ToString("yyyy-MM-ddTHH:mm:ssK", CultureInfo.InvariantCulture));
+            }
         }
 
         public override void WriteValue(byte[] value)

tests/Squidex.Infrastructure.Tests/MongoDb/BsonConverterTests.cs

@@ -87,7 +87,7 @@ namespace Squidex.Infrastructure.MongoDb
                     Bool = true,
                     Byte = 0x2,
                     Bytes = new byte[] { 0x10, 0x12, 0x13 },
-                    DateTimeOffset = DateTime.UtcNow.Date,
+                    DateTimeOffset = DateTime.Today,
                     DateTime = DateTime.UtcNow.Date,
                     Float32 = 32.5f,
                     Float64 = 32.5d,
@@ -126,17 +126,35 @@ namespace Squidex.Infrastructure.MongoDb
         }
 
         [Fact]
-        public void Should_serialize_to_iso()
+        public void Should_serialize_datetime_to_iso()
         {
             source.DateTime = new DateTime(2012, 12, 12, 12, 12, 12, DateTimeKind.Utc);
-            source.DateTimeOffset = new DateTime(2012, 12, 12, 12, 12, 12, DateTimeKind.Utc);
 
             var target = JObject.FromObject(source).ToBson();
 
             Assert.Equal("2012-12-12T12:12:12Z", target["DateTime"].ToString());
+        }
+
+        [Fact]
+        public void Should_serialize_datetimeoffset_to_iso_utc()
+        {
+            source.DateTimeOffset = new DateTime(2012, 12, 12, 12, 12, 12, DateTimeKind.Utc);
+
+            var target = JObject.FromObject(source).ToBson();
+
             Assert.Equal("2012-12-12T12:12:12Z", target["DateTimeOffset"].ToString());
         }
 
+        [Fact]
+        public void Should_serialize_datetimeoffset_to_iso_utc_with_offset()
+        {
+            source.DateTimeOffset = new DateTimeOffset(2012, 12, 12, 12, 12, 12, TimeSpan.FromHours(2));
+
+            var target = JObject.FromObject(source).ToBson();
+
+            Assert.Equal("2012-12-12T12:12:12+02:00", target["DateTimeOffset"].ToString());
+        }
+
         [Fact]
         public void Should_write_problematic_object()
         {