timedatectl

Overview

timedatectl views and changes the system clock, timezone, RTC settings, and NTP synchronization on systemd systems. Prefer it over ad-hoc date -s for persistent timezone and NTP policy. On Ubuntu Server, default NTP is often systemd-timesyncd; some hosts use chrony instead — enable one cleanly, not both fighting.

Syntax

timedatectl [options] [command]

Common Commands / Options

Command / option	Description
status	Show time, TZ, NTP state (default)
show	Machine-readable properties
list-timezones	All zone names
set-timezone Zone	Set timezone (e.g. UTC, America/New_York)
set-time 'YYYY-MM-DD HH:MM:SS'	Set clock manually (disable NTP first if required)
set-ntp true\|false	Enable/disable NTP (systemd unit)
set-local-rtc 0\|1	RTC in UTC (0, recommended for Linux) or local
-H host / --machine=	Remote/container via systemd
--no-ask-password	Non-interactive privilege

Key Use Cases

1. First-boot timezone + NTP setup
2. Verify clock sync before Kerberos/TLS-sensitive work
3. Switch TZ for multi-region servers (prefer UTC on servers)
4. Diagnose “TLS not yet valid” / log timestamp skew

Examples with Explanations

Status

timedatectl
timedatectl status

Shows local time, universal time, RTC, timezone, and whether NTP is active/synchronized.

Machine-readable

timedatectl show
timedatectl show -p Timezone -p NTP -p NTPSynchronized --value

Good for scripts and monitoring checks.

List and set timezone

timedatectl list-timezones | grep -i america
timedatectl list-timezones | grep -i '^Asia/'
sudo timedatectl set-timezone UTC
sudo timedatectl set-timezone America/New_York
timedatectl

Server fleets usually standardize on UTC; set human TZ only when local wall time is required.

Enable NTP (systemd-timesyncd path)

sudo timedatectl set-ntp true
timedatectl
systemctl status systemd-timesyncd --no-pager
# Ubuntu may use:
systemctl status systemd-timesyncd.service

set-ntp true lets systemd enable the appropriate time-sync unit.

Chrony hosts

# If chrony is the chosen stack:
sudo apt install chrony
sudo systemctl enable --now chrony
# timedatectl should still report NTP synchronized when chrony steps/slews correctly
chronyc tracking
chronyc sources -v
timedatectl

Don’t leave timesyncd and chrony both active and conflicting — pick one source of truth.

Manual time (maintenance / air-gap)

sudo timedatectl set-ntp false
sudo timedatectl set-time '2026-08-09 12:00:00'
# re-enable NTP when network is available:
sudo timedatectl set-ntp true

Manual set is a last resort; large steps can confuse databases and cert validation.

RTC in UTC (recommended on Linux)

timedatectl | grep -i rtc
sudo timedatectl set-local-rtc 0

Dual-boot with Windows may fight over local vs UTC RTC — document the choice on shared hardware.

Verify sync health

timedatectl | grep -iE 'ntp|time zone|synchronized'
# timesyncd:
timedatectl timesync-status 2>/dev/null || true
journalctl -u systemd-timesyncd -n 20 --no-pager
# chrony:
chronyc tracking 2>/dev/null || true

“System clock synchronized: yes” is the headline for TLS and distributed systems.

date interaction

date
date -u
date --iso-8601=seconds
timedatectl

date formats the current clock; timedatectl manages policy (TZ/NTP/RTC).

Understanding Output

Typical timedatectl status fields:

Field	Meaning
Local time	Wall time in current TZ
Universal time	UTC
RTC time	Hardware clock reading
Time zone	IANA zone name + offset
System clock synchronized	Whether systemd believes sync is good
NTP service	active/inactive
RTC in local TZ	n = UTC (preferred on Linux-only)

timedatectl show exposes properties like Timezone=, NTP=, NTPSynchronized=, TimeUSec=.

Notes & Pitfalls

• Prefer NTP over permanent manual set-time on networked hosts.
• Containers often inherit host time and cannot change the host clock; TZ can still be set in-process via TZ env.
• Cloud images may already enforce UTC + timesync — cloud-init can reapply settings.
• Large backward clock jumps break make, systemd units, and DB leases — prefer slewing via NTP.
• Kerberos and TLS are intolerant of multi-minute skew.
• set-timezone does not rewrite historical log timestamps already written.
• Virtual hardware RTC quality varies; NTP remains mandatory for accuracy.

Related Commands

• date — print/format time
• hwclock — read/set hardware clock directly
• chronyc / chronyd — chrony stack
• ntpdate — legacy one-shot (avoid on modern systemd; use chrony/timesyncd)
• hostnamectl — host identity companion on first boot
• timedatectl timesync-status — timesyncd detail when available

Additional Resources

• man timedatectl
• man systemd-timesyncd.service
• man chrony.conf (when using chrony)