> UTC is not a time zone, it is a standard. UTC is also not GMT (Greenwich Mean Time), rather, UTC has replaced GMT. UTC is more precise; the term 'GMT' is ambiguous.
That document goes to great lengths to keep this distinction between time scales and time formats. They're different, and conflating them will get you very confused. When you describe a time in PST, you are almost certainly using UTC.
This is just not correct. The "Z" is a historical maritime designation for the zero-point timezone, GMT, and predates UTC by decades.
UTC is defined by the International Telecommunications Union in recommendation TF.460-6 (pdf link: https://www.itu.int/dms_pubrec/itu-r/rec/tf/R-REC-TF.460-6-2...). It's brief and you won't find any mention of time zones.
The symbolism "UTC+0" or the "Z" timezone come from ISO-8601, which is a specification for how to represent times in strings. You can find that specification here: https://web.archive.org/web/20171019211402/https://www.loc.g...
See section 2.1.12 Note 3:
> UTC is not a time zone, it is a standard. UTC is also not GMT (Greenwich Mean Time), rather, UTC has replaced GMT. UTC is more precise; the term 'GMT' is ambiguous.
That document goes to great lengths to keep this distinction between time scales and time formats. They're different, and conflating them will get you very confused. When you describe a time in PST, you are almost certainly using UTC.