How does this API deal with political timezone and DST changes? Will JavaScript versions come with an updated hardcoded database in the spec, or browser updates, or will it require internet connection to get it from some server? What if 2 clients or a client and a server have different versions of this database, could inconsistency issues arise? Will all past changes keep being handled correctly (e g. if a region changed their timezone or DST rules multiple times in the past, does it take this into account for any past date)? How will the date math work on future dates where the DST rules are not yet known (e.g. could a future date change its display or UTC value after an update)?
Temporal specifies using IANA Timezone Database for all time zone aware implementations and recommends them to "include updates to the IANA Time Zone Database as soon as possible." Moreover:
> If implementations revise time zone information during the lifetime of an agent, then which identifiers are supported, the primary time zone identifier associated with any identifier, and the UTC offsets and transitions associated with any Zone, must be consistent with results previously observed by that agent.
Basically, the timezone data must not change while a browser tab, a Node program, or a service worker is running.
AFAIK, this does not prevent possible timezone data mismatch between different versions of browser and server, or even different browsers on the same machine.
