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Strangely accurate RTC time on Debian

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Logan:
Hi friends.
One of my PC's RTC only drift 0.3 seconds over 15 days, and it even correct itself sometimes (so it's not always faster or slower).
It's so strange because it's using a similar configuration compare to another PC, which drift ~10 seconds per day...
There's no ntpd installed, how can I check if there's any software syncing time for me, or is this RTC just happens to be so accurate?
Thank you for reading.

RoGeorge:
In Ubuntu (which is a customised Debian) the time synchronization is on by default.  Try this from a terminal:
timedatectl status

Nominal Animal:
Instead of ntpd, systemd uses systemd.timesyncd service.

Even though you don't have ntpd or anything similarly named running, you do have an ntpd client-only systemd.timesyncd service running.

Logan:
Thank you both.
Here's some CLI results:

~$ timedatectl status
               Local time: Thu 2024-05-16 22:32:31 UTC
           Universal time: Thu 2024-05-16 22:32:31 UTC
                 RTC time: Thu 2024-05-16 22:32:31
                Time zone: UTC (UTC, +0000)
System clock synchronized: no
              NTP service: n/a
          RTC in local TZ: no

~$ timedatectl timesync-status
Failed to query server: The name org.freedesktop.timesync1 was not provided by any .service files

~$ timedatectl show-timesync
Failed to parse bus message: No route to host

~$ timedatectl show
Timezone=UTC
LocalRTC=no
CanNTP=no
NTP=no
NTPSynchronized=no
TimeUSec=Thu 2024-05-16 22:32:45 UTC
RTCTimeUSec=Thu 2024-05-16 22:32:45 UTC

~$ systemctl status systemd.timesyncd
Unit systemd.timesyncd.service could not be found.

Still seems not synced...

SiliconWizard:
Yep. systemd-based distributions rarely use ntpd, although you can use it instead of systemd.timesyncd if you prerfer. That's what I had set up myself, but it turned out that ntpd was much slower to update time than timesyncd for some reason, so I eventually resorted to timesyncd.

Also to answer the OP, not all RTCs on motherboards are born equal. 10 seconds per day of RTC drift is about 115 ppm, which is about average (not good) for a *basic* crystal-based oscillator, and proof in itself that it's not network-synced.

But 0.3 s of drift over 15 days would be 0.23 ppm, which, while not completely impossible with a good TCXO, is completely unlikely to be what you get with any consumer PC RTC, so it's evidently network-synced.

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