The hub follows your time zone's rule and changes its own clock. Nothing is lost, nothing is counted twice, and the prices stay attached to the right hours.
The detail is worth knowing, though, because the changeover touches three things at once: the clock, the records and the tariff zones.
How the hub knows about the change
It stores the full time-zone rule, not a fixed offset — a string like CET-1CEST,M3.5.0,M10.5.0/3, which carries the transition dates. The presets in Settings → Time for European and US zones are rules of this kind, so a hub set from a preset handles the change by itself, every year, with nothing to do in March or October.
Two things to watch:
- A fixed offset never changes. If the hub's zone is entered as a plain offset, it keeps that offset through the year. There is also a Daylight saving flag in the raw configuration editor — it has no effect. Only the rule string decides. Use a preset, or enter a proper rule.
- Southern-hemisphere zones with DST — Sydney, Auckland, Santiago — are not among the app's presets and aren't detected from your browser. The hub itself handles their rules correctly; entering one is the awkward part today.
What happens to the records
Hourly records are keyed by UTC, which is what keeps the night tidy:
- In autumn the repeated local hour is two different UTC hours, so you get two separate records — both kept, neither overwriting the other.
- In spring no hour is missing from the data. The local label simply jumps from 01:59 to 03:00.
Day, week and month records follow your local calendar. So the changeover day really is 23 hours in spring and 25 in autumn, and the week and month containing it are an hour shorter or longer. That's correct, not a glitch: it's the amount of time that actually passed.
One visible side effect: an hourly chart drawn in local time shows one hour label twice in autumn, and skips one in spring.
What happens to the cost
Every 15-minute quarter is priced by the local time at its midpoint, so energy always gets the zone it genuinely fell in.
For a night zone running 23:00–07:00, that means the window simply lasts nine hours on the autumn night and seven on the spring one. The repeated hour in autumn is real energy and is priced at the night rate, like the hour before it.
The one rough edge: a zone boundary set inside the hour that repeats or disappears — a window ending at 02:30, say — will be active twice for that half hour in autumn, and in spring its edge lands at 03:00. Whole-hour boundaries outside 02:00–03:00, which is nearly every real tariff, are unaffected.
And the daily counters
They roll at local midnight, which the changeover doesn't move — European and US transitions happen between 01:00 and 03:00. The day's totals then cover 23 or 25 hours of real energy, and the hub's day marker carries the new offset from the following day.
Verified against the firmware's self-tests, which run the record and pricing code against real Berlin, New York and Sydney transition dates. Not observed on a live changeover.