timedatectl

Control the system time and date

timedatectl [options …] {command}

query and change the system clock and its settings.

Use systemd-firstboot(1) to initialize the system time zone for mounted (but not booted) system images.

--no-ask-password 
--adjust-system-clock If set-local-rtc is invoked the system clock is synchronized from the RTC Otherwise, the RTC is synchronized from the system clock.
-H
--host=
Execute the operation remotely. Specify a hostname, or a username and hostname separated by "@", to connect to. The hostname may optionally be suffixed by a container name, separated by ":", which connects directly to a specific container on the specified host. This will use SSH to talk to the remote machine manager instance. Container names may be enumerated with machinectl -H HOST.
-M
--machine=mid
Execute operation on a local container. Specify a container name to connect to.
--no-pager Do not pipe output into a pager like more
commands
status Show current settings of the system clock and RTC, including whether network time synchronization is on, by systemd-timesyncd.service.
if this command shows the status as off, a different service might synchronize the clock
 timedatectl status
               Local time: Thu 2019-09-05 18:37:49 EDT
           Universal time: Thu 2019-09-05 22:37:49 UTC
                 RTC time: n/a
                Time zone: America/New_York (EDT, -0400)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no
set-time ccyy-mm-dd hh:mm:ss system clock and RTC
set-timezone tz Set the system and RTC zone time. Alters /etc/localtime symlink. See localtime(5) for more information.
list-timezones List time zones includes:
Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
…
America/Antigua
America/Araguaina
America/Argentina/Buenos_Aires  (Argentina is the only contaninent/country with citys )
…
Europe/Berlin
Europe/Bratislava
…
Pacific/Tongatapu
Pacific/Wake
Pacific/Wallis
UTC(only abbreviation)
set-local-rtc 0|1 0, maintain the RTC in universal time.
1, maintain the RTC in local time prefered.
also synchronize the RTC from the system clock, unless --adjust-system-clock changes /etc/adjtime
set-ntp 0|1 active, enabled and starts, or disables and stops systemd-timesyncd.service
aka systemctl enable --now systemd-timesyncd.service and
systemctl disable --now systemd-timesyncd.service, but is protected by a different access policy.

systemd-timesyncd.service also ensures a monotonic clock on systems without RTC even if no network is available. See systemd-timesyncd.service(8) for details about this.

-h
--help
 
--version version string and exit.

ENVIRONMENT

Pager to use when --no-pager is not given; overrides $PAGER. If neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known pager implementations are tried in turn, including less(1) and more(1), until one is found. If no pager implementation is discovered no pager is invoked. Setting this environment variable to an empty string or the value "cat" is equivalent to passing --no-pager.
$SYSTEMD_PAGER Override the options passed to less (by default "FRSXMK").
$SYSTEMD_LESS Override the charset passed to less (by default "utf-8", if the invoking terminal is determined to be UTF-8 compatible).
$SYSTEMD_LESSCHARSET

EXAMPLES

           $ timedatectl set-ntp true
           ==== AUTHENTICATING FOR org.freedesktop.timedate1.set-ntp ===
           Authentication is required to control whether network time synchronization shall be enabled.
           Authenticating as: user
           Password: ********
           ==== AUTHENTICATION COMPLETE ===

           $ systemctl status systemd-timesyncd.service
            systemd-timesyncd.service - Network Time Synchronization
              Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled)
              Active: active (running) since Mo 2015-03-30 14:20:38 CEST; 5s ago
                Docs: man:systemd-timesyncd.service(8)
            Main PID: 595 (systemd-timesyn)
              Status: "Using Time Server 216.239.38.15:123 (time4.google.com)."
              CGroup: /system.slice/systemd-timesyncd.service
                      595 /lib/systemd/systemd-timesyncd
           ...

See

systemd(1), hwclock(8), date(1), localtime(5), systemctl(1), systemd-timedated.service(8), systemd-timesyncd.service(8), systemd- ntpd firstboot(1