Daylight saving and “X ago”
What happens to an hours-ago or 1-day-ago lookup when the lookback window contains a DST change, and when to prefer an explicit timestamp.
DST
Offsets follow the device zone, not a fixed UTC minus
This site subtracts milliseconds from the current Date in your browser. Around a spring-forward or fall-back, “24 hours ago” still means 24 × 60 minutes of elapsed time, which may or may not look like the same clock time yesterday in other software.
If you are filling a timesheet in a zone that changed overnight, read the timezone label and the date under the clock. Do not assume the hour number is enough.
When an offset is the wrong tool
If the event has a known civil time (“Tuesday 09:00 after the change”), write that datetime. Use the time difference calculator with two explicit local times. An offset phrase hides the DST seam.
If you are reconstructing a global launch, send UTC. The UTC grid on each result page is a check, not a lock to UTC.
What this site will not do
It will not apply historical zone revisions your browser does not know. It will not insert leap seconds. Those limits are on the disclaimer because they matter when someone tries to use a toy calculator as a legal clock.
Questions
Did my 8-hour shift lookup go wrong last night?
If DST fell back, eight elapsed hours can span a local clock that repeated an hour. Trust the weekday and UTC offset on the result, or log the UTC time.