On Sep 30, 2016, at 8:43 AM, Paul Eggert <eggert@cs.ucla.edu> wrote:
The issue is not limited to updating tzdata version. It can also occur when the system changes the wall-clock time zone, e.g., by changing /etc/localtime to point to a different file. On mobile devices this can occur when you (say) cross the Trammell Bridge from Blountstown to Bristol in Florida, to go from "slow time" (CST) to "fast time" (EST).
For what it's worth, Darwin (macOS, iOS, etc.) will detect at least some time zone changes and the next localtime() call will use the new zone. (And a MacBook * counts as a "mobile device" in this scenario, although it has to use Wi-Fi to find out where it's located, as MacBook *'s don't have GPS receivers built in.) I don't *think* it has any provisions for handling updates to the tzdb, but Apple doesn't currently distribute those except as part of Software Updates, as far as I know, and those require a reboot. (I seem to remember this coming up in a past discussion of the timeliness of tzdb updates and of vendors doing tzdb updates separate from OS dot-dot version updates.)