All there is mentioned is

       ${HOME}/.tzlist could be edited by hand, with a valid value for the TZ variable on each line.

Please add a separate TZLIST(5) man page, giving the full format.
E.g., it turns out one can add # comments.

OK it turns out # won't comment, but instead just creates a mess.
Therefore please also make it comment.
It is really inconvenient not to have any way to add comments.

Dear submitter,

as the package gworldclock has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1120757

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)