See current timezone setting:
sudo zdump /etc/localtime # /etc/localtime Wed Mar 14 09:46:46 2012 MDT strings /etc/localtime # MST7MDT,M3.2.0,M11.1.0 (and other garbage)
Set timezone for all users:
mv /etc/localtime /etc/localtime.original # cp /usr/share/zoneinfo/America/Boise /etc/localtime ln -sfn /usr/share/zoneinfo/America/Denver /etc/localtime
Set time zone for current user:
In Linux, most timezone information is controlled by GLIBC, which relies on the file /etc/localtime. Different distributions do different things with this file; some have it as a symbolic link to the proper timezone definition file (usually in /usr/share/zoneinfo), but most have it as an actual, explicit file.
Verifying the Timezone File 
zdump is a small program that is part of GLIBC. It dumps the information about a given timezone file. If you want to verify what the Daylight Savings times are for a given year with a given file, you can do something like this:
$ zdump -v /etc/localtime | grep 2007
The -v tells zdump to display timezone information for all transitions rather than just the current date.
date Sun May 2 15:49:55 MDT 2010
ENVIRONMENT TZ Specifies the timezone, unless overridden by command line parameters. If neither is specified, the setting from /etc/localtime is used.
Time zones are kept here:
Files have access, modify and change times.
- access time (atime): time the file was last accessed
- modify time (mtime): file modification times
- change time (ctime): status change times
$ stat test/ File: `test/' Size: 4096 Blocks: 8 IO Block: 4096 directory Device: 900h/2304d Inode: 20987905 Links: 2 Access: (0700/drwx------) Uid: ( 1068/ kenneth) Gid: ( 1068/ kenneth) Access: 2010-09-20 11:30:01.000000000 -0600 Modify: 2010-09-20 11:14:45.000000000 -0600 Change: 2010-09-20 11:14:45.000000000 -0600
List file times:
$ ls -lt $ ls -ltr # reverse
-t mtime - modification time -u atime - access time -c ctime - change time
America Time Zones
# cat /etc/timezone Etc/UTC
Universal UTC Zulu Etc/UTC US/Central America/Chicago US/Eastern America/New_York US/Hawaii Pacific/Honolulu US/Mountain America/Denver US/Pacific America/Los_Angeles
# date Sat 16 Feb 15:46:56 UTC 2019 # TZ=America/Denver date Sat 16 Feb 08:47:01 MST 2019
Linux date time timezone