How to check which timezone in Linux?

If you mean from the console, just type:

date +%Z

If you want the numeric timezone:

date +'%:z %Z'

Sample output:

-05:00 EST

I wanted to find the timezone in "US/Eastern" or "Europe/London" form instead. You can find this in:

• /etc/timezone (present on Ubuntu and Red Hat? but not e.g. Amazon Linux)
• (on Red Hat style systems) as ZONE="US/Eastern" in /etc/sysconfig/clock

• or you can try and match /etc/localtime to one of the files under /usr/share/zoneinfo; annoyingly this doesn't seem to be a symlink, but you can e.g.

  cd /usr/share/zoneinfo
  find * -type f -exec sh -c "diff -q /etc/localtime '{}' > /dev/null && echo {}" \;

  to find matching files - there's probably better ways to do that, but that works. There will be multiple matches.