Is Linux /usr/share/zoneinfo/ platform agnostic?

Question

My embedded Linux program needs to convert UTC time to local time for a report saved in a text file. The most obvious way to do this is to use the API function strftime().

However... on my system, the following code does not work during Daylight Saving time - the resultant time is off by an hour:

char        dateTimeOut[128] = { 0 };
bool        isError = false;
struct tm   timeValue = { 0 };

do {
    if (0 > mktime(&timeValue)) { isError = true; break; }
    isError = 0 == strftime(&dateTimeOut[0], sizeof(dateTimeOut), "%a %d %b %Y %T", &timeValue);
} while (false);

My embedded platform is a Linux (ARM/busybox) system. It has systemd and the timedatectl system executable, but it does not have /etc/timezone, /usr/share/zoneinfo/, nor the zic timezone data compiler program.

I have plenty of system disk space on this embedded system.

Is it possible to copy the /usr/share/zoneinfo contents from an amd64 Linux implementation to my embedded ARM Linux implementation "as-is" to get access to the timezone functionality that timedatectl and strftime() provide?

Answer 1

I ended up creating a tarball of /usr/share/zoneinfo/ from an Ubuntu system, copied it and unzipped it on the embedded system, and the following "just worked."

So it seems the /usr/share/zoneinfo is platform agnostic.

root@mityomapl138:~# timedatectl set-timezone America/New_York
root@mityomapl138:~# timedatectl
Warning: ignoring the TZ variable, reading the system's timezone setting only.

      Local time: Thu 2024-01-18 11:13:37 EST
  Universal time: Thu 2024-01-18 16:13:37 UTC
        RTC time: Thu 2024-01-18 16:13:37
        Timezone: America/New_York (EST, -0500)
     NTP enabled: n/a
NTP synchronized: yes
 RTC in local TZ: no
      DST active: no
 Last DST change: DST ended at
                  Sun 2023-11-05 01:59:59 EDT
                  Sun 2023-11-05 01:00:00 EST
 Next DST change: DST begins (the clock jumps one hour forward) at
                  Sun 2024-03-10 01:59:59 EST
                  Sun 2024-03-10 03:00:00 EDT