/usr/share/postgresql/9.6/timezonesets/ is in postgresql-9.6 9.6.11-0+deb9u1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/postgresql/9.6/timezonesets/Africa.txt
/usr/share/postgresql/9.6/timezonesets/America.txt
/usr/share/postgresql/9.6/timezonesets/Antarctica.txt
/usr/share/postgresql/9.6/timezonesets/Asia.txt
/usr/share/postgresql/9.6/timezonesets/Atlantic.txt
/usr/share/postgresql/9.6/timezonesets/Australia
/usr/share/postgresql/9.6/timezonesets/Australia.txt
/usr/share/postgresql/9.6/timezonesets/Default
/usr/share/postgresql/9.6/timezonesets/Etc.txt
/usr/share/postgresql/9.6/timezonesets/Europe.txt
/usr/share/postgresql/9.6/timezonesets/India
/usr/share/postgresql/9.6/timezonesets/Indian.txt
/usr/share/postgresql/9.6/timezonesets/Pacific.txt