A day on Mars lasts 24 hours 39 minutes 35 seconds from one sunrise to the next, about 40 minutes longer than a day on Earth, and it has its own name: a sol. Measured against the stars instead of the Sun, Mars turns once in 24 hours 37 minutes 23 seconds. A Mars year lasts 668.6 sols, or 687 Earth days, and its four seasons run from 142 to 194 sols because the orbit is eccentric. Mars Rally Championship, a free browser rally game, still runs its daily challenge on Earth days.
How long is a day on Mars, in hours and minutes
A Martian solar day lasts 24 hours 39 minutes 35.244 seconds, or 24.66 hours, according to the technical notes behind NASA's Mars24 clock. Scientists call it a sol, a term adopted for the Viking landers in 1976, so that "day" can go on meaning the Earth one.
Mars also has a shorter day. Its sidereal day, one full turn measured against the stars, lasts 24 hours 37 minutes 22.663 seconds. The difference is orbital: in the time Mars spins once, it also moves about 1/670 of the way round the Sun, so it must turn for another 2 minutes 13 seconds before the Sun is back in the same place in its sky. Earth's shorter year makes its gap wider, nearly four minutes: 23 hours 56 minutes 4 seconds against 24 hours.
The sol is the day that governs the ground: when the Sun rises, when solar panels charge, when a rover wakes. Mission clocks split it into 24 Mars hours, and each one lasts 61 minutes 39 seconds. At the equator the Sun is up for about half of every sol, roughly 12 hours 20 minutes.
The sol also paces the sky. Phobos orbits in 7 hours 39 minutes, fast enough to rise in the west and set in the east about twice a sol, while Deimos takes 30 hours 18 minutes and drifts the other way; what Phobos and Deimos look like from the surface of Mars covers that sky. Most sols end with a blue glow around the setting Sun, for reasons why sunsets on Mars are blue explains.
Mars time vs Earth time, side by side
Mars keeps almost Earth's hours and almost Earth's tilt, then stretches everything else.
| Mars | Earth | Mars vs Earth | |
|---|---|---|---|
| Solar day, sunrise to sunrise | 24 h 39 min 35 s (one sol) | 24 h | 39 min 35 s longer (2.7%) |
| Sidereal day, one turn against the stars | 24 h 37 min 23 s | 23 h 56 min 4 s | 41 min 19 s longer |
| One hour, a 24th of the solar day | 61 min 39 s | 60 min | 1 min 39 s longer |
| Year | 668.6 sols, or 687 Earth days | 365.24 days | 1.88 Earth years |
| Axial tilt | ≈25.2° | ≈23.4° | about 1.8° more |
| Orbital eccentricity | ≈0.093 | ≈0.017 | more than 5× |
| Longest season | Northern spring, ≈194 sols (≈199 days) | Northern summer, ≈94 days | about 2.1× as long |
| Shortest season | Northern autumn, ≈142 sols (≈146 days) | Northern winter, ≈89 days | about 1.6× as long |
| Year numbering | Mars Year 39 begins 30 Sep 2026 | 2026 | Mars Year 1 began 11 Apr 1955 |
One sol is 1.0275 Earth days. The season lengths are NASA's, named for the northern hemisphere; the southern hemisphere runs the other way round.
How long is a year on Mars
A year on Mars lasts 687 Earth days, according to NASA's Mars facts page. That is 668.6 sols, or 1.88 Earth years: Mars orbits about 1.5 times farther from the Sun than Earth does, on a longer path at a lower speed.
Planetary scientists date Martian events by solar longitude, written Ls, the angle Mars has travelled along its orbit since its northern spring equinox, rather than by sol count. Ls 0° opens northern spring, 90° northern summer, 180° northern autumn and 270° northern winter, so a date in Ls names its season outright; the Laboratoire de Météorologie Dynamique's page on solar longitude sets out the system.
Years get numbers too. By the count planetary scientists use, Mars Year 1 began on 11 April 1955, and Mars Year 39 begins on 30 September 2026.
To convert an age, divide it by 1.88: a 30-year-old has lived just under 16 Mars years, or about 10,660 sols.
Is there a Mars calendar?
Not an official one. Sols, Ls and Mars Year numbers are all the bookkeeping a robot needs. The best-known proposal for people is the Darian calendar, drawn up by aerospace engineer Thomas Gangale in 1985: 24 months of 27 or 28 sols. Science fiction patched the clock instead: in Kim Stanley Robinson's novel Red Mars, clocks stop at midnight for the leftover 39 and a half minutes, a pause the settlers call the timeslip.
How long is a season on Mars
A season on Mars lasts between 142 and 194 sols, roughly twice as long as a season on Earth, and the four are badly unequal. NASA's figures for the northern hemisphere: spring 194 sols, summer 178, autumn 142, winter 154.
Tilt makes the seasons; the orbit sets their lengths. Mars leans 25.2°, close to Earth's 23.4°, so its hemispheres take turns facing the Sun for the same reason ours do. But its orbit is more than five times as eccentric as Earth's, and a planet moves fastest when it is closest to the Sun. Mars passes perihelion late in northern autumn, shortly before the southern summer solstice, so northern autumn and winter go by quickly. It is farthest out, and slowest, in northern spring, which drags on for 194 sols, 52 more than autumn. On Earth, the longest season beats the shortest by under five days.
The south gets its summer close to the Sun, short and comparatively warm, and its winter far away, long and cold; the north gets the milder version of both. Southern summer, near perihelion, is dust storm season, the subject of Mars dust storms explained.
How rover teams live on Mars time
A rover works to the Sun, so at first its team works to the rover. For the first 90 sols of Curiosity's mission in 2012, as the Spirit and Opportunity teams had in 2004, the operations team at NASA's Jet Propulsion Laboratory lived on Mars time: each shift started at the same Martian hour, which put it 39 minutes 35 seconds later on the Earth clock every day.
After about 18 sols, a shift that started at 9 a.m. starts at 9 p.m. After about 36 sols, or 37 Earth days, it has gone all the way round the clock and starts at breakfast again. Ninety sols is about two and a half laps.
Then the team returns to Earth hours and lets the two clocks slide past each other. When they line up badly, data from the rover's last sol arrives too late in the working day to plan the next sol from it; Curiosity's team calls those restricted sols. On Fridays, one plan covers three sols to carry the rover through the weekend. The teams even have their own words: tosol for today, yestersol for yesterday.
Sol 0 or sol 1
Missions do not agree on where to start counting. Spirit and Opportunity called their landing day sol 1. Curiosity and Perseverance call theirs sol 0, so Curiosity's sol 5,000, on 29 August 2026, was the 5,001st sol it had seen on Mars, about 14 Earth years after landing. Perseverance reached sol 1,890 on 14 June 2026, the day it passed marathon distance; how many rovers are on Mars has the rest of the roll call.
What time is it on Mars right now
It depends where you stand, but Mars has its own counterpart of UTC. Coordinated Mars Time, or MTC, is the mean solar time at the Martian prime meridian, which runs through the small crater Airy-0. The crater honours George Biddell Airy, whose Greenwich telescope fixes Earth's prime meridian, and NASA's Mars24 software calls the same time Airy Mean Time. The Mars24 Sunclock shows it live, with the local times at landers and rovers.
Curiosity and Perseverance each keep local mean solar time at their own longitude, a time zone with one resident. Jezero Crater lies about 60 degrees of longitude west of Gale Crater, so Perseverance's clock runs about four Mars hours behind Curiosity's: 8 a.m. at Jezero is noon at Gale.
For dates there is the Mars Sol Date, a running count of sols since 29 December 1873 and Mars' answer to the Julian date. The epoch predates the close approach of 1877, when Asaph Hall discovered both moons, and is by coincidence the birthday of the astronomer Carl Otto Lampland. Mars Sol Date 54,295 began on 26 September 2026.
Does Mars Rally Championship run on Mars time?
No. The daily challenge in Mars Rally Championship follows your local calendar date: every pilot gets the same seeded stage and sky for the day, and it resets at your midnight. A daily on sols would reset 39 minutes 35 seconds later every day and lap your clock every 37 days, a schedule rover teams put up with for 90 sols and a daily race has no reason to copy.
The numbering follows Spirit and Opportunity, not Curiosity: the shareable result card counts 1 January 2026 as Daily #1, and there is no Daily #0. Streaks count Earth days as well, so the 30-day streak achievement, MARTIAN RESIDENT, takes 29.2 sols.
The sky does not keep a sol either: each run keeps the sky it starts with, and the daytime sun drifts but never sets. Night comes up on about 26% of dailies, with Phobos and Deimos on orbits shortened to about 6 and 24 hours of game time. One honest miss: the two in-game moons cross the sky in the same direction, where on Mars Phobos rises in the west and Deimos in the east.
Where to try this
- Today's daily challenge: one seeded stage and sky for every pilot, resetting at your local midnight rather than on a sol.
- Every Mars Rally Championship achievement, including the streak ladder that tops out at MARTIAN RESIDENT.
- Mars Rally Championship is free and runs in a browser tab with no download and no account, on a laptop, a phone in landscape or a school Chromebook, and up to eight pilots can race the same stage live.