Community dedicated to the international standard YYYY-MM-DD date format.
I suspect the T acts as a delimiter. D is unnecessary, because the date is at the beginning of the string. And then Z is another delimiter, to separate the time from the timezone.
EDIT: I think I misunderstood your question, but I'll leave my post, in case it's useful to others when considering the sections of a full timestamp.
I think you're probably right. If the format was
DATETTIMEZTIMEZONE
And you omit DATE you still have TTIME
Hmmm those are good points. I feel this gels well with how in the syntax for durations / periods all unit delimiters are mandatory (also because they're tail) when the unit is present and the header / marker is P.
I have always found the uppercase T/Z delimiters to make the timestamp less human-readable.
Maybe because spaces aren't available in some contexts (like URL's) and you don't need both T and D to make it more easily recognizable.
The short answer I believe is that ISO 8601 is a Date format so we expect date but not time. Thats my take. I think it's important to include timezone if you have time thought tbh