Set the hub to the time zone you actually live in. Everything dated follows from that.
In Settings → Time the hub takes a time zone, and the app offers your browser's as a suggestion. It's a suggestion, not a sync: the hub keeps its own setting, and that setting is what every record is filed against.
Where a day starts
At local midnight in the hub's time zone. The daily counters roll there, and so do the figures the app labels "today" — Economics even names the source, showing the period as today (hub clock).
Set the zone correctly and the hub's day matches yours. Leave it on something else and your days will roll at an odd hour: a hub left on UTC in a UTC+8 country starts its day at 08:00, and every "today" figure covers the wrong sixteen hours.
Months work the same way: calendar months in the hub's own zone.
Why it matters beyond dates
Tariff zones are resolved against the hub's clock too — not your computer's and not Home Assistant's. A hub in the wrong time zone shifts every zone boundary by the offset, so energy gets priced at the wrong rate while the app looks perfectly normal.
That's the real reason to get this right: a wrong hour on a chart is obvious, a wrong price is not.
Worth checking after setup
- Settings → Time shows the clock synchronized.
- The time zone is yours, not the default.
- Open the week by zones on the Tariffs page and confirm the zones land where you expect them to.
Until the hub has synchronized, it still picks a zone from whatever time it believes it is — so check the clock before trusting the first costs.