The issue looks to be the TZDIR (Time zoneinfo directory) has changed between
10.12 and 10.13
On 10.12 (Sierra), /usr/include/tzfile.h defines:
$ grep TZDIR /usr/include/tzfile.h
#ifndef TZDIR
#define TZDIR "/usr/share/zoneinfo" /* Time zone object file directory */
#endif /* !defined TZDIR
HelloCommand-Click shows the Swift representation of Objective-C API in Xcode. I understand that Darwin overlay which defines the Foundation APIs is here: https://github.com/apple/swift/tree/master/stdlib/public/SDK/FoundationAlso, there is:
