On an embedded Debian ARM system for which I am programming the C localtime function returns the UTC time rather than the local time. I searched the Net and found out this was because the TZ environment variable is not set.

Booting into other Linux distros ( Ubuntu, Fedora ) I notice that the TZ environment variable is not set for myself as a login user, and yet the 'date' command gives the local time correctly.

Can someone tell me why a Linux distro which does not have the TZ environment variable set gives the correct local time when I issue the 'date' command but the embedded Debian ARM system for which I am programming, which also has no TZ environment variable set, gives me the UTC time when I issue the 'date' command ?

The question is how I get the embedded Debian ARM system to have the correct local time. Maybe I need to ask that on some Debian forum, but I thought I would try here to try to get some insight into this problem.

Not sure what the problem is, but maybe the timezone man page will help:

None of my desktop systems set the TZ environment variable. If TZ is not set then date uses the default system rules which is /etc/timezone.

Is the timezone database installed on your embedded system? Does /usr/share/zoneinfo exist?

Yes /usr/share/zoneinfo does exist.

I found out that using the command:

timedatectl set-timezone some_time_zone

will permanently set the time zone for the system.

Thanks for your help !