Time zones and “what time was it”
Why the answer depends on your device zone, how to read the UTC grid, and how to share an offset without confusing someone in another country.
Time zones
The result is always local to the browser
This site does not guess your city from IP. It reads the timezone the operating system already set. “7 hours ago” in Tokyo and “7 hours ago” in New York are different civil times. That is the correct behavior for a personal log and the wrong behavior for a global launch instant.
The header on every result shows the IANA zone name and the numeric UTC offset so you can see which clock was used.
The UTC grid
Under the main answer, each result page lists the same instant in a set of UTC offsets. Use that when a teammate asks “what time was that for me?” You still need to know their offset; the grid does not replace a named zone like America/Chicago.
If two people open the same /3-hours-ago link, they do not see the same HH:MM. They each see three hours before their own now. To share one instant, send the UTC time or a full datetime with offset.
Daylight saving
When a lookback window contains a DST transition, “subtract 24 hours” and “subtract one calendar day” can disagree in other software. This site uses a millisecond offset from the current Date object, so it follows whatever rules your JavaScript engine applies for that zone.
If you are reconstructing an event around a spring-forward gap, prefer an explicit timestamp over an offset phrase.
Questions
Can I lock the calculator to UTC?
Not as a site setting. Switch your device timezone, or read the UTC+0 row in the grid. Most people asking “what time was it” want the local clock.