Take into account timezone information changes #1

dimich commented 2026年06月10日 10:03:11 +02:00

There are two variants how timezone may change:

1. User changed /etc/localtime symlink target.
2. tzdata file content changed due to software upgrade.

Options to implement the handling:

• Call tzset() every time before conversion to local time
  Cons:

  • In "minute" mode changes are applied only for next minute.
  • Doesn't seem to work for 2nd variant of change (TODO: research).
  • Extra syscall for each tick even if timezone info is not changed.

• Watch /etc/localtime and/or tzfile changes with inotify(7).
  Cons:

  • Need to replicate glibc behavior for case when TZ variable is set.
  • Need to track full tzdata file path: any component of the path may change.

• Watch org.freedesktop.timedate1 D-Bus property changes (TODO: research).
  Cons:

  • Limited to freedesktop.org compliant systems.
  • Depends on D-Bus and systemd service.

• Trigger tzfile re-read externally from package manager hook and timezone selection tools.
  Cons:

  • Specific to package manager.
  • "Timezone selection tools" is a vague concept.

There are two variants how timezone may change: 1. User changed `/etc/localtime` symlink target. 2. tzdata file content changed due to software upgrade. Options to implement the handling: * Call `tzset()` every time before conversion to local time Cons: - In "minute" mode changes are applied only for next minute. - Doesn't seem to work for 2nd variant of change (TODO: research). - Extra syscall for each tick even if timezone info is not changed. * Watch `/etc/localtime` and/or tzfile changes with inotify(7). Cons: - Need to replicate glibc behavior for case when `TZ` variable is set. - Need to track full tzdata file path: any component of the path may change. * Watch `org.freedesktop.timedate1` D-Bus property changes (TODO: research). Cons: - Limited to freedesktop.org compliant systems. - Depends on D-Bus and systemd service. * Trigger tzfile re-read externally from package manager hook and timezone selection tools. Cons: - Specific to package manager. - "Timezone selection tools" is a vague concept.