None. What for? From what I've witnessed over the last two decades is that there is no official acceptance of type 2+ headers which from this angle looks to be the most used. Besides why tackle a new idea if we can't get the even the simplest things right such as telling the difference between a number and a string.
Just saying ... :-)
ml> until you convert it to a number for the necessary math when ml> needed ;)
Sure. I'd appreciate seeing your routine for taking care of that, esecially considering given the potentially corrupted (eastern) utc offset. Myself I will continue ignoring it ... after I send this reply that is.
ml> their string representation to some sort of numeric ml> representation so they can be added or subtracted from a time ml> value to give the time in another location...
You don't even have to do that if you use strftime() and a suitable offset.