As you pointed out, there are, at the time of writing, no timezones that have a Universal Time offset greater than 24 hours. This would occur when a governmental body declares it. Support for +/- 167 hours was likely added in Version 3 to handle that possibility. Consider that these offsets are specified by governmental decree, so the authors of this standard/code probably imagined that a bureaucrat may want to shift their timezone by nearly 1 week since 167 hours = 6 days and 23 hours. This is referring to both the UT Offset listed in the ttinfo entries, and to the POSIX.1-2017-style TZ string ().