Comment 5 for bug 1887107

After some quick investigation, I found that gnome-control-center pulls its data directly from the zone.tab file, just like Paul Eggert warned against doing in the comment I quoted above.

in tz.h (https://github.com/GNOME/gnome-control-center/blob/5532301ce76d2719c1105c61f576abe7fae2dc16/panels/datetime/tz.h)

# define TZ_DATA_FILE "/usr/share/zoneinfo/zone.tab"

in tz.c (https://github.com/GNOME/gnome-control-center/blob/5532301ce76d2719c1105c61f576abe7fae2dc16/panels/datetime/tz.c)

static gchar *
tz_data_file_get (void)
{
 gchar *file;

 file = g_strdup (TZ_DATA_FILE);

 return file;
}

[...]

TzDB *
tz_load_db (void)
{
 g_autofree gchar *tz_data_file = NULL;
 TzDB *tz_db;
 FILE *tzfile;
 char buf[4096];

 tz_data_file = tz_data_file_get ();
 if (!tz_data_file) {
  g_warning ("Could not get the TimeZone data file name");
  return NULL;
 }
 tzfile = fopen (tz_data_file, "r");
 if (!tzfile) {
  g_warning ("Could not open *%s*\n", tz_data_file);
  return NULL;
 }

 tz_db = g_new0 (TzDB, 1);
 tz_db->locations = g_ptr_array_new ();

 while (fgets (buf, sizeof(buf), tzfile))
 {
  [PARSING CODE].
 }

 fclose (tzfile);

 /* now sort by country */
 sort_locations_by_country (tz_db->locations);

 /* Load up the hashtable of backward links */
 load_backward_tz (tz_db);

 return tz_db;
}