The TZ variable may either contain a direct timezone representation, or
a reference to a file in tzfile(5) format. Mapping a direct timezone
representation to a Windows timezone would be difficult.
According to tzset(3), a file reference should start with a colon, though
glibc treats it as optional. It may be an absolute path or a path relative
to /usr/share/zoneinfo. Adjust winpr_detect_windows_time_zone to accept
either.
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