Sunset lighting automation started running an hour late after the clocks changed Troubleshooting

Start with the timezone the process is running in, not the one the interface displays.

If you are running in a container, the app can be configured with your local timezone while the container itself has no TZ set and thinks it is UTC. Most things still look right because the app converts for display, but anything that depends on the underlying clock, including sun calculations in some setups, quietly works in the wrong frame. An hour is exactly what a daylight saving mismatch looks like.

Things to check in order:

• date inside the container versus on the host
• the TZ environment variable on the container
• whether the host's tzdata package is out of date, which happens on machines that have not been updated in a year
• whether your latitude and longitude are still set, since a wiped location can silently fall back to a default

Fixed clock times still working is consistent with this, because those are evaluated in local time by the app itself.

Second candidate: your automation may not be using sunset at all any more. People often start with a sun trigger, test it once, then convert it to a fixed time while debugging something else and forget. Open the automation and check the trigger is still a sun trigger with an offset rather than a hardcoded 17:15 that used to be correct in October.

Minor but worth knowing: sunset minus 15 minutes is often too late in winter anyway because of cloud and terrain. Once you fix the hour, you may find you want minus 30 in the winter months. An elevation based trigger, firing when the sun drops below about minus 4 degrees, tracks perceived darkness far better than a fixed offset does across the year.

Also confirm the clock on the machine is actually being synced. A Pi with no battery backed clock and a broken NTP config drifts, and I have seen a box sit an hour out after a power cut because it restored a stale time and never corrected. timedatectl will tell you in one line whether NTP is active and synchronised.