NTP Check — How Far Your Clock Has Drifted
This queries a time server and reports the offset between its clock and yours. It is a small measurement with disproportionate consequences, because a surprising amount of infrastructure assumes that clocks agree and fails in unhelpful ways when they do not.
Why run it
Because clock drift produces symptoms nobody attributes to the clock. Certificate validation fails because a certificate appears not yet valid or already expired. Token-based authentication rejects credentials that are perfectly correct. Log correlation across hosts becomes impossible because events appear in the wrong order. Scheduled jobs fire at the wrong time or twice. Every one of those gets investigated as a problem with the failing system, and the actual cause is a machine that is four minutes fast.
Why automate it
Drift is gradual by definition, so there is never a moment when something breaks and prompts you to check. It crosses a threshold quietly and then several unrelated things start failing at once, which is a distinctly unpleasant way to spend an evening. A scheduled check with an alert on offset catches it at seconds rather than minutes, and it also detects the more common modern failure: time synchronisation that has stopped running entirely, where drift is slow enough to take weeks to matter and total once it does.
What it gives you
Prevention for a whole family of failures that are never diagnosed as time problems. The check is trivial and the alternative is investigating authentication, certificates and scheduling separately before someone thinks to look at the clock.