People expect e.g. their "daily power consumption" to end at midnight local time. When they zoom in on the daily aggregates, they don't want a spike to suddenly

People expect e.g. their "daily power consumption" to end at midnight local time. When they zoom in on the daily aggregates, they don't want a spike to suddenly disappear just because it belonged to the next local day and you only stored UTC-day aggregates. Even more so for billing.