Thanks...
I don't fully understand what your code does, or what language is it in... I am doing this from C#.
The problem is that, due to the way this is implemented, I don't have a way to validate if a value is null prior to building the object that will be used to send the API request for the operation.
More than getting some fix (if anyone has it, it will be welcome) I would like to know or understand why this happens in custom objects but not in standard objects, and why it happens only for datetime fields and not for other datatypes...