Bug#1150416: Resubmit | NTP sync issue | systemd-timesyncd

[Krisztian.Kormondi at t-systems.com]

Package: systemd-timesyncd
Version: 259.7-3gl1+bp2150


To whom it may concern,

We experienced a significant system clock issue on several Debian virtual machines using systemd-timesyncd.

The incident occurred between 2026-10-08 02:26:51 CEST and 2026-10-08 04:42:53 CEST, corresponding to 2026-10-08 00:26:51 UTC and 2026-10-08 02:42:53 UTC.

Environment

  *
Operating system: Debian 14(forky)
  *   Virtualization: QEMU/KVM managed by libvirt
  *   Clock source: kvm-clock
  *   NTP client: systemd-timesyncd

Observed behavior

The affected virtual machines experienced an apparent forward clock jump of approximately 33 days. The machines then operated with the incorrect future date for approximately two hours and sixteen minutes.

Afterward, systemd-timesyncd corrected the clock backward by exactly:

-2851200 seconds

This is equal to:

-33 days

Our clock-jump monitor reported:

JUMP -2851200.0s at epoch 1791427373; ntp_synced=yes

The correction occurred at approximately:

2026-10-08 02:42:53 UTC
2026-10-08 04:42:53 CEST
Journal evidence

The journal contains the following messages:

Nov 10 00:26:34 systemd-resolvedClock change detected. Flushing caches.

Oct 08 02:42:36 systemd-resolvedClock change detected. Flushing caches.

Oct 08 02:42:36 systemd-journaldTime jumped backwards, rotating.

NTP config
All of the machines which were affected were synced against the following IP  152.53.239.75

Could you please check if there was everything ok with the NTP server?

Thank you in advance


Kind regards
Krisztián Körmöndi
DEUTSCHE TELEKOM AG
Deutsche Telekom Systems Solutions Slovakia  s.r.o.
Enterprise Application Services- Open Sovereign Cloud
Krisztián Körmöndi
DevOps Engineer
Moldavska cesta 8B, 04001 Kosice; Slovakia
Web: www.deutschetelekomitsolutions.sk<https://www.deutschetelekomitsolutions.sk/>
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