UTC — the one time scale every eclipse is quoted in
UTC is the single time scale this site computes in. Eclipse times are quoted in it because an event crossing a dozen zones needs one common reference.
Coordinated Universal Time is the time scale every instant on this site is computed in before it is shown to you. Eclipse times are quoted in UTC by long convention.
Why not local time
Because an eclipse is a single event, three hours or so from end to end, crossing a dozen time zones — and no local time describes it. Two observers a few hundred kilometres apart may be in different zones, or on different sides of a daylight-saving boundary, so quoting their contact times locally can make moments a few minutes apart look an hour and a few minutes apart, and moments an hour apart look simultaneous.
One scale removes that entirely. The timings panel shows both — UTC and your device's local time — with UTC first, because it is the one that can be compared with anything published anywhere else. The eclipse lists are UTC only.
The three letters
UTC is a compromise between the English word order and the French, which is why it matches neither. It is not translated anywhere on this site: the same three letters appear in every language, so a time on a page and a time in the app can be compared without decoding a label.
Two things it is worth knowing UTC is. It is an atomic scale, not an astronomical one: it is kept within 0.9 seconds of the Earth's actual rotation by the occasional insertion of a leap second, which is why it drifts from uniform time in one-second steps rather than smoothly. And it is what GMT became — for every purpose on this site the two are the same thing, and UTC is the name to use. It never observes daylight saving.
What this site does not correct for
The Earth's rotation is not perfectly uniform, and the difference between it and a uniform time scale — ΔT — is measured after the fact and not predictable far ahead. Predictions here do not correct for it at all.
This is not only a problem for the distant future. ΔT is already about seventy seconds, so every track on this site is drawn something like 30 km west of where it belongs, today, before any other source of error. A minute of ΔT is roughly 25 km of longitude at the equator. Over centuries it grows to many minutes and the displacement grows with it.
Thirty kilometres is a fraction of a typical path width, so the maps are sound for deciding where to travel. They are not sound for deciding where the edge of the path is, and this is one of the reasons the limits carry the warning they do.
Related
Updated 13 August 2026.