I'm going to profoundly disagree with you here. These are not open-standards. These are not self-documenting, csv, receiver-has-to-guess formats. These are two

I'm going to profoundly disagree with you here. These are not open-standards. These are not self-documenting, csv, receiver-has-to-guess formats. These are two on-board non critical systems talking to each other. The main requirement is that the format be specified. A desirable trait is that the format be easy to implement. Sorry, ISO 8601, you're too complicated for the task. Integrating a library to handle it is already too hard, too risky and over-engineering. You'd have to either trust it to be bug-free or heavily test it. KISS, remember?