Star Map by Date
Enter a date — any date — and see the sky as it stood that night over any place on Earth.
Pick a date and see its sky
Free, in your browser, with no account and nothing to buy. The SVG, the 300 dpi PNG and the PDF (a real page of the size you pick, from 21 × 29.7 cm to 70 × 100 cm) are each the complete poster.
The night sky is a calendar. Because Earth orbits the sun, the stars rise about four minutes earlier every night; over a year the sky at a fixed hour makes one complete turn. A January midnight and a July midnight share almost no constellations — the date genuinely changes the picture.
This generator converts your date to a Julian Date and sidereal time, then computes the position of every catalog star for that night. Time and place matter too: the same date over Sydney and over London gives two different skies, which is why the form asks for all three.
Picking the right moment
- Date — the calendar date at the place, not in your current timezone.
- Time — defaults to 21:00, a natural “evening sky” hour. For a specific event, use the event’s hour.
- After midnight? A night that ran into the small hours belongs to the next calendar date — a common mix-up worth double-checking.
What the chart draws
The chart holds the 1,630 stars brighter than magnitude 5.0 and the 89 constellation figures, and the Milky Way is drawn as a soft band. The Moon is drawn in its real phase, and left off when it was below your horizon. The five naked-eye planets, Mercury, Venus, Mars, Jupiter and Saturn, are drawn where they stood. The Sun is drawn too whenever it was up, and the caption says whether your moment was daylight, twilight or full dark: the stars are always drawn where they stood, even when daylight or twilight hid them. So is an eclipse, if your moment falls inside one. Uranus, Neptune and 133 deep-sky objects are one switch away: tick Deep-sky objects and the chart marks the Messier objects and southern showpieces and adds Uranus and Neptune (see them over London on a winter evening). Great comets since 1900 can be added (Hale-Bopp over London, 1997). Not drawn: faint comets and satellites, whose orbits this tool does not compute. Every position is carried to your date by precession. Not modelled: the stars’ own proper motion. A date before 15 October 1582 is read in the Julian calendar. It all runs in your browser, nothing is uploaded, and the downloads are complete and free. Accuracy, print sizes and privacy, answered in full.
Common questions
How far back or forward can the date go?
Any date from 1 January of year 1 to 31 December 3000. Dates before 15 October 1582 are read in the Julian calendar, the way they were written at the time, and a switch beside the date takes a date that has already been converted to Gregorian instead — in 1066 the two differ by six days. Stars, constellation lines, the Milky Way, the Moon, the Sun and the planets are all carried to the sky of that date by long-term precession, which by 1066 amounts to 13° of the equinox's slide. What is not modelled is the stars' own proper motion: over 2,000 years it moves Alpha Centauri 2.1°, Arcturus 1.3° and Sirius and Procyon 0.7° each, and every other first-magnitude star less than 0.4°. Outside years 1 to 3000 the page says so in one sentence instead of drawing a chart.
Does the time of day matter?
Yes — the sky rotates 15° per hour, so an evening chart and a 3 a.m. chart of the same date look substantially different. If you only care about the date, the 21:00 default is a good representative evening sky.
Is the sky the same on that date every year?
For the fixed stars, almost exactly — the same date and clock time repeats to within about a degree year over year. The Moon does not repeat: its phase and place are recomputed for the exact moment you enter, so the same calendar date a year later shows a different Moon. Nor do the planets: Mercury, Venus, Mars, Jupiter and Saturn are drawn where they stood that night, and each keeps its own calendar — Jupiter moves about one zodiac constellation a year, Saturn one every two and a half, and Venus returns to the same place in the evening sky only every eight years. The Sun is drawn too when the moment you pick is in daylight, and the line under the chart names the light: daylight, twilight or full dark.