On a server you have no option but to get time right.

All servers on the Internet synchronize to Coordinated Universal Time – UTC – via NTP. UTC is a derivative of International Atomic Time

Time is expressed in many different ways. Typically a computers time is displayed in the local timezone.

See also:

• DJB on time

Time formats

Current local time / UTC

The following formats current UTC time in seconds resolution

• ISO 8601
• RFC 3339 = ISO 8691 with T instead a space between date and time
• RFC 2822

date -uIs
date -u --rfc-3339 s
date -uR

For local time just omit the u

tai64n

TAI64 is used in ?multilog and ?svlogd logfiles.

Read/follow a multilog logfile in local time:

<logfile tai64nlocal | less -S
tail -F logfile | tai64nlocal

tai64nlocal comes with daemontools.

Notes:

• Use TZ= on the commandline to get timestamps in UTC. This does not work currently (01/2019) with diet libc compiled daemontools.

Synchronization

Pool

We use time servers from the NTP pool.

On portable computes the global servers are the best choice, on stationary equipment – like servers – use the respective zone, e.g.:

• Germany

Client software

systemd.timesyncd

Newer Debian uses systemd and comes with systemd-timesyncd which uses the global servers by default. Configure other pool zones within /etc/systemd/timesyncd.conf

For Germany: [[!format Error: unsupported page format tcsh"""]]

After configuration restart timesyncd:

service systemd-timesyncd restart

Check the status of timesyncd:

systemctl status systemd-timesyncd

Check time synchronization in general:

timedatectl

Disable timesyncd:

systemctl stop systemd-timesyncd
systemctl disable systemd-timesyncd

No uninstallation is possible, since it is integrated into systemd.

Chrony

chrony is the ntp client of choice on other systems.

Configure it in /etc/chrony/chrony.conf.

Check the configuration

chronyc sources

. The starred server is the one selected for synchronization.

You can speed up synchronization with:

chronyc
chronyc> passwd <password from /etc/chrony/chrony.keys>
chronyc> burst 10/10

Check synchronization status:

chronyc tracking

.

Newer chronys allow to specify a pool as well as the iburst directive to get faster on track:

pool 0.de.pool.ntp.org iburst
pool 1.de.pool.ntp.org iburst
pool 2.de.pool.ntp.org iburst
pool 3.de.pool.ntp.org iburst

Virtual Servers

Some virtualizations force the hwclock to the host time. If that is synchronized the guest does not need network synchronization

Hetzner vCloud

Based on KVM, seems to be in good sync. Nontheless, the Debian image installs systemd-timesyncd, although it is not configured to the Hetzner NTP servers.