If the file specification filespec is omitted, or its value cannot be interpreted, then Coordi‐
nated Universal Time (UTC) is used. If filespec is given, it specifies another tzfile(5)-format
file to read the timezone information from. If filespec does not begin with a '/', the file
specification is relative to the system timezone directory. If the colon is omitted each of the
above TZ formats will be tried.