Question

One of the nastiest problems working across time zones 🙂

Here is my problem:

1. I have code that passes date into WCF via JSON object and I use “short” format where it contains only milliseconds since 1970 with no time zone. This DateTime parsed by WCF just FINE

2. I store date into SQL Server Database. Example: 2011-06-07 22:17:01.113 – date as I see it in SQL Server and this is perfectly fine since I store everything in UTC. So, it’s (-5) time zone and date looks right.

3. I load date field into my object using EF and inside object property says it is 22:17 and Kind=Unspecified which is OK again, it is loaded from SQL, I know it is UTC but code doesn’t know that so it loads this date as Unspecified.

4. I return this object to WCF client. It can be XML or it can be JSON. Here is what happen. When I JSON(this is what client specifies) – I get this: 1307503021113-0500 for date. If we convert first portion to DateTime using SQL:

SELECT DATEADD(ss, 1307503021,
‘1970-01-01’)

2011-06-08 03:17:01.000

Part above already wrong, no? If we apply -5hr adjustment we will be back to 22:17pm which already utc time? This part already confusing to me. But what even worse – when I deserialize using JavaScriptSerializer – I see DateTime value in newly inflated object saying UTC kind and 3:17am

var oSerializer = new JavaScriptSerializer();
                var returnValue = (T)oSerializer.Deserialize(s, typeof(T));

I’m all puzzled already and I wonder if it’s possible to force WCF and other serializer/deserializers to NOT do any time offsets and stuff? I’d rather format all dates for display manually and I want to store UTC dates in database.

UPDATE:

Looks like WCF thinks that if DateKind is Unspecified than it’s LOCAL.
I did this: After I got objects from EF I specified Kind:

foreach (var tu in tripUpdates)
                {
                    tu.DeviceTime = DateTime.SpecifyKind(tu.DeviceTime, DateTimeKind.Utc);
                }

That fixed it – now when WCF serves object it doesn’t include timezone which is GREAT. Now my main question is there any way to specify Kind on EF entities somehow so I don’t have to manually specifiy kind for every date in service?

Answer 1

When you get the datetime via a SELECT statement always set the DateTime.Kind to UTC. This way WCF/XML will not try to adjust the time.