Doesn't work with custom converters

[Darkvater]

I don't think this solution works as-is with custom serializera for ValueTypes such as DateTime. It is marked by the system as ValueType and as such will receive a Nullable type. If your custom converter is not aware of that it will not be able to convert. This is quite a corner case scenario as normally you would just use the Newtonsoft.DateTimeFormatString. However if you need to deserialise from one format string and serialise to another you can't use global settings for example.