World clock for 100 cities, with sunrise, twilight, the moon and an orrery
Everywhere at once.
Your time --:--:--
A board of world clocks — drawn analog faces beside their digital reading — for any of 100 cities on a hand-kept register, each told through the real IANA time zone your own browser carries, so a half-hour zone reads half past and Kathmandu reads its famous :45. Each face wears the sky over that city right now: day, twilight or night, worked out from the sun’s actual altitude.
Below the clocks, an observatory: sunrise, sunset and civil twilight for any city on the register, the moon inked at its current phase, and an orrery of the eight planets you can scrub fifty years either way. Every figure on this page is computed by the page itself, from published astronomical arithmetic — nothing arrives over a wire, so nothing here can break in an outage.
100 cities on the register · 18 dials · 12 sets of hands · the browser’s own IANA zones · NOAA solar arithmetic · a J2000 orrery · zero requests
The clocks
A hundred cities. Every continent.
The board deals thirty-two of them, taken round-robin across the regions so it reaches Africa and South America before it reaches the Americas twice — six Antarctic research stations are on the register, and they keep real time on real clocks. It is yours after that: add any city the register knows, retire the ones you don’t watch, walk a clock left or right, and hover one to see where on the earth it actually is. The arrangement is remembered in this browser and nowhere else.
World clocks
winding…
Spin for a fresh thirty-two cities out of the hundred on the register, a dial for every clock out of eighteen, and hands for every clock out of twelve.
Dial—
Hands—
Focus takes the arrows, the cross and the three lines of type off every card and prints the city on the dial instead — where a watch carries its maker’s name, under twelve — with the time where a sub-dial goes, at six. It travels into a popped window with the board.
The sky over each city — day, civil twilight or night, from the sun’s computed altitude — is the word under the time and the hairline along the top of the card. The arrows walk a clock along the board, × retires it, and the arrow on a card opens that one clock in a window of its own. Ticks pause while the tab is hidden. Right-click a clock — or long-press, or ⋯ — for everything it can do; ⌘/Ctrl-click to pick several, and right-click between the clocks for the board’s own menu.
The bench
Ten instruments, to the hundredth.
Stopwatches and countdowns, run together, each with its own start, lap and reset. Nothing counts up: every reading is worked out from a stamp, so a stopwatch left running in a background tab comes back with the right number rather than a slow one, and a countdown is aimed at a moment on the wall clock rather than at a tally of ticks.
Right-click a stopwatch — or long-press it, or its ⋯ — for everything it can do; ⌘/Ctrl-click to pick several, and Start, Stop or Lap them on one stamp, at the same instant. Right-click between the cards for the whole bench.
The sun
Today’s daylight, worked out by hand.
Pick a city and the page computes its day: civil dawn, sunrise, solar noon, sunset, civil dusk — drawn as an arc of today’s daylight with the sun placed where it is this minute. Computed with the NOAA solar equations, in your browser, from nothing but the date and the register’s coordinates. The moon has a section of its own below.
The sky desk
Sun times carry the NOAA algorithm’s honest error — a minute or two at mid-latitudes, a few more near the poles, where a degree of refraction is a long stretch of horizon. All times are the city’s own, from its IANA zone.
The moon
Tonight’s moon, photographed and then lit.
The same photographed, arithmetically lit moon, beside the clocks. Its own page, The Moon, adds twelve months of phases and every eclipse among them.
The moon
What comes next
Right-click the moon — or long-press it, or press ⋯ — to step it by the hour or the week, jump to the next full or new moon, copy its figures, or save it as a PNG, a PDF or a print.
The orrery
Eight planets, fifty years either way.
A drawn orrery: every planet placed at its computed heliocentric longitude for the date on the scrub, from the JPL mean orbital elements at epoch J2000. Drag the scrub and watch Mercury whip round eight-hundred-odd times while Neptune barely clears a third of its orbit.
The orrery
Not to scale — the spacing between orbits is drawn for reading, not measured; the angles are the computed positions. Elements are the JPL/Standish J2000 table, stated valid 1800–2050 — the outer years of the scrub lean on its slow, known drift. Orbits are drawn as circles; the real ellipses are within a few percent of round.
Overview
A hundred cities in eighty-one countries.
The register behind the clocks is a hundred cities in eighty-one countries: 25 in Asia, 22 in Europe, 16 in Africa, 13 in South America, 11 in North America, 7 in Oceania, and six research stations in Antarctica. Eight of them keep time off the whole hour — St John’s, Tehran, Mumbai, Delhi, Kathmandu, Colombo, Yangon and Adelaide — which is exactly where a clock that assumes whole-hour zones goes wrong, and these do not.
To compare two places, put both on the board and read them side by side. To plan around the light, choose a city on the sky desk and read the day’s five marks, from the first light of civil twilight to its last. To time something, the bench runs up to ten stopwatches and countdowns at once, and a countdown can be aimed at a moment days, weeks, months or years away. The board, the sky city and the bench stay in this browser, and a link can hand a city or an orrery date to somebody else.
The day in more detail — golden hour, the three twilights and a whole year of daylight — is on The Sun. Tonight’s moon has a page of its own, The Moon, with twelve months of phases and eclipses. And one date worth counting down to belongs on Deadline.
About
Nothing here can go down.
The time in 100 cities at once, each clock set by the time-zone rules your own browser carries, so daylight saving time and half-hour zones come out right. Pick a city for its civil dawn, sunrise, solar noon, sunset and civil dusk, worked out with NOAA’s solar equations and good to a minute or two away from the poles. The moon is drawn at its true phase, computed from its position rather than from an average month, and the orrery places the eight planets for any date within fifty years either way. Ten stopwatches and countdowns run to the hundredth of a second. None of it is downloaded after the page loads, so it keeps working offline.
Every other instrument on labs.llc reads a wire, and says so. This one is the exception, and that is its whole flex: zero upstream. No feed, no key, no proxy — not one figure on this page arrives over a wire. The page computes everything it shows, so an outage anywhere on earth cannot blank a single number. Load it once and it works on an airplane.
The clocks are the browser’s own: Intl.DateTimeFormat against real IANA zone names, which is the same tz database — DST rules, half-hour zones, Nepal’s :45 — that your operating system keeps current. The register of 100 cities is hand-kept in the page: name, zone, coordinates, country, continent — nothing else. Every zone on it has been checked against the tz database itself, and the continent is stored rather than guessed from the zone name, because the zone name is not a continent: America/ covers two of them, Atlantic/Reykjavik is Europe, and Pacific/Honolulu is Oceania in a country most of which is not.
The sun figures use the NOAA solar position equations — declination and the equation of time from the Julian century, rise and set at zenith 90.833°, civil twilight at 96° — good to a minute or two at mid-latitudes, honestly worse near the poles. The moon is computed, not averaged: Meeus’s lunar theory for its position and distance and his solar theory for the sun’s, with the phase taken from the angle between them — the moon’s longitude good to about ten arcseconds and the phase instants to about a minute. This page used to read the moon off the mean synodic month, which is a fair description of an average and a poor one of any particular night: over 2026–27 the mean runs up to fourteen hours away from the true phase, and it is more than six hours out for three nights in four. The drawn disc is a geocentric view with north up; libration is not modelled, so features near the limb sit where they average rather than where they are tonight. The orrery runs on the JPL approximate Keplerian elements — Standish’s J2000 table with per-century rates, stated valid 1800–2050 — with Kepler’s equation solved on each scrub. What the arithmetic cannot honestly say, the page does not draw.
Your board of clocks and your chosen sky city are remembered in this browser and nowhere else. A link to the page can carry a city or an orrery date with it.