“Syncthing version 1.x will soon be replaced by Syncthing version 2.x.
Version 2 brings a new database format and various cleanups, but remains
protocol compatible with Syncthing 1.”
Aloha! Indeed, the language is being cleaved by such oversights. You can be in charge of overlooking this issue, effective ahead of two weeks from now. We'll peruse your results and impassionately sanction anything you call out (at least when it's unravelable). This endeavor should prove invaluable. Aloha!
Now that I'm back at my desk I had to check ISO8601, that suffix is not included. However it does look like an extension - RFC 9557 - which looks like is still in proposed state.
I would personally caution using these suffixes until wider adoption, because AFAIK the Olson database names themselves are not standardised on non-POSIX systems (i.e you might have a hard time on Windows).
Aha! Yeah the last time I needed to play with timezones I had map between Olson and Windows's proprietary names. Looks like they came out their NIH Syndrome:
"Proposed" is the final state of many stable RFCs; see a list at [1], and compare it to the (much shorter) list of finished standards above it. The name is kind of misleading these days. Some discussion at [2]. Just to give an example, the base64 RFC 4648 is also a "proposed standard".
https://github.com/syncthing/syncthing/releases/tag/v1.30.0