REST API DateTime formatting

It *appears* (I may be mistaken, obviously) that the DateTime field "created_at" returns a different formatted string when doing a Create, rather than when doing a Read. The Newtonsoft JSON desrializer doesn't like the Create format (it's fine with the Read format). I could specify a specific format override, but going down this rout doesn't mean all DateTime fields will always be in the same format, so I thought I'd ask first 

Is there a reason for this?

Is there a way around this?

Would I be better off having the JSON target fields as strings instead of DateTime properties?

Any alternative proposals?