diff --git a/src/NATS.Client.Core/INatsSerialize.cs b/src/NATS.Client.Core/INatsSerialize.cs
index 82f815a9e..3b4819d06 100644
--- a/src/NATS.Client.Core/INatsSerialize.cs
+++ b/src/NATS.Client.Core/INatsSerialize.cs
@@ -116,7 +116,7 @@ public void Serialize(IBufferWriter<byte> bufferWriter, T value)
         {
             if (value is DateTime input)
             {
-                if (Utf8Formatter.TryFormat(input, span, out var written))
+                if (Utf8Formatter.TryFormat(input, span, out var written, new StandardFormat('O')))
                 {
                     bufferWriter.Advance(written);
                 }
@@ -133,7 +133,19 @@ public void Serialize(IBufferWriter<byte> bufferWriter, T value)
         {
             if (value is DateTimeOffset input)
             {
-                if (Utf8Formatter.TryFormat(input, span, out var written))
+                bool result;
+                int written;
+                if (input.Offset == TimeSpan.Zero)
+                {
+                    // This will make it place `Z` instead of `+00:00` at the end
+                    result = Utf8Formatter.TryFormat(input.UtcDateTime, span, out written, new StandardFormat('O'));
+                }
+                else
+                {
+                    result = Utf8Formatter.TryFormat(input, span, out written, new StandardFormat('O'));
+                }
+
+                if (result)
                 {
                     bufferWriter.Advance(written);
                 }
@@ -392,7 +404,7 @@ public void Serialize(IBufferWriter<byte> bufferWriter, T value)
             if (buffer.Length == 0)
                 return default;
 
-            if (Utf8Parser.TryParse(span, out DateTime value, out _))
+            if (Utf8Parser.TryParse(span, out DateTime value, out _, 'O'))
             {
                 return (T)(object)value;
             }
@@ -405,7 +417,7 @@ public void Serialize(IBufferWriter<byte> bufferWriter, T value)
             if (buffer.Length == 0)
                 return default;
 
-            if (Utf8Parser.TryParse(span, out DateTimeOffset value, out _))
+            if (Utf8Parser.TryParse(span, out DateTimeOffset value, out _, 'O'))
             {
                 return (T)(object)value;
             }
diff --git a/tests/NATS.Client.Core2.Tests/SerializerTest.cs b/tests/NATS.Client.Core2.Tests/SerializerTest.cs
index eabc317df..f63c7a746 100644
--- a/tests/NATS.Client.Core2.Tests/SerializerTest.cs
+++ b/tests/NATS.Client.Core2.Tests/SerializerTest.cs
@@ -68,8 +68,9 @@ public async Task NatsMemoryOwner_empty_payload_should_not_throw()
     public void Utf8_serializer()
     {
         SerializeDeserialize<string>("foo", "foo");
-        SerializeDeserialize<DateTime>(DateTime.MinValue, "01/01/0001 00:00:00");
-        SerializeDeserialize<DateTimeOffset>(DateTimeOffset.MinValue, "01/01/0001 00:00:00 +00:00");
+        SerializeDeserialize<DateTime>(new DateTime(1970, 12, 31, 23, 42, 2, DateTimeKind.Utc), "1970-12-31T23:42:02.0000000Z");
+        SerializeDeserialize<DateTimeOffset>(new DateTimeOffset(1970, 12, 31, 23, 42, 2, TimeSpan.Zero), "1970-12-31T23:42:02.0000000Z");
+        SerializeDeserialize<DateTimeOffset>(new DateTimeOffset(1970, 12, 31, 23, 42, 2, TimeSpan.FromHours(1)), "1970-12-31T23:42:02.0000000+01:00");
         SerializeDeserialize<Guid>(Guid.Empty, "00000000-0000-0000-0000-000000000000");
         SerializeDeserialize<TimeSpan>(TimeSpan.Zero, "00:00:00");
         SerializeDeserialize<bool>(true, "True");