[please cc me, I am not subscribed] Hello, I have been working on Util-linux' hwclock and other GNU/Linux date-time issues. I have a couple of questions that I hope someone here can answer. The tz database file system tree was changed on May 25 1998, moving 'right' and 'posix' from subdirectories of zoneinfo to sibling directories. However GNU libc continued to use the old structure until it stopped including the data files on Mar 7 2012. Now some Linux distributions are still using the old subdirectory tree structure. Is there a reason that the old tree structure is still being used? Does it break something to have 'right' and 'posix' as sibling directories? I ask because the problems that were the catalyst for the change in 1998 are still happening. It seems to me like it was a good solution, but nobody used it. If I may ask one more favor, could you please review the information below which I have added to the hwclock man-page? I still need to include information about using TZDIR. Thank you very much, William POSIX vs 'RIGHT' A discussion on date-time configuration would be incomplete without addressing timezones, this is mostly well covered by tzset(3). One area that seems to have no documentation is the 'right' directory of the IANA Time Zone Database, aka tz, aka zoneinfo. There are two separate databases in the zoneinfo system, posix and 'right'. 'Right' (now named leaps) includes leap seconds and posix does not. To use the 'right' database the System Clock must be kept in UTC + leap_seconds, i.e., TAI - 10. This allows calculating the exact number of seconds between two dates that cross a leap second epoch. The System Clock is then converted to the correct civil time, including UTC, by using the 'right' timezone files which subtract the leap sec- onds. Note: this configuration is considered experimental and is known to have issues. To configure a system to use a particular database all of the files located in its directory must be copied to the root of /usr/share/zoneinfo. Files are never used directly from the posix or 'right' subdirectories, e.g., TZ='right/Europe/Dublin'. This habit was becoming so common that the upstream zoneinfo project restructured the system's file tree by moving the posix and 'right' subdirectories out of the zoneinfo directory and into sibling directories: /usr/share/zoneinfo /usr/share/posix /usr/share/leaps Unfortunately, some Linux distributions are changing it back to the old tree structure in their packages. So the problem of system administra- tors reaching into the 'right' subdirectory persists. This causes the system timezone to be configured to include leap seconds while the zoneinfo database is still configured to exclude them. Then when an application such as a World Clock needs the South_Pole timezone file; or an email MTA, or hwclock needs the UTC timezone file; they fetch it from the root of /usr/share/zoneinfo , because that is what they are supposed to do. Those files exclude leap seconds, but the System Clock now includes them, causing an incorrect time conversion. Attempting to mix and match files from these separate databases will not work, because they each require the System Clock to use a different timescale. The zoneinfo database must be configured to use either posix or 'right', as described above.