🔴 Mars Date Converter
Earth date ↔ Mars year/sol/Ls using the Allison & McEwen algorithm (the same one behind NASA’s Mars24).
Earth Date (UTC)
Time (UTC)
—
Mars Year
—
Sol of Year
—
Month
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Ls (Solar Longitude)
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Mars Sol Date
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Mars Time (MTC)
Mars Year
Ls (0–360°)
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Earth Date (UTC)
—
Julian Date
Mars Months and Seasons
| Month | Ls, ° | Sol of Year | Note |
|---|---|---|---|
| 1 | 0–30 | 0.0–61.2 | Northern Hemisphere Spring Equinox |
| 2 | 30–60 | 61.2–126.6 | — |
| 3 | 60–90 | 126.6–193.3 | Aphelion (greatest Sun distance) |
| 4 | 90–120 | 193.3–257.8 | Northern Hemisphere Summer Solstice |
| 5 | 120–150 | 257.8–317.5 | — |
| 6 | 150–180 | 317.5–371.9 | — |
| 7 | 180–210 | 371.9–421.6 | Northern Autumn Equinox · dust storm season begins |
| 8 | 210–240 | 421.6–468.5 | Dust storm season |
| 9 | 240–270 | 468.5–514.6 | Perihelion (smallest Sun distance) · dust storms |
| 10 | 270–300 | 514.6–562.0 | Northern Winter Solstice · dust storms |
| 11 | 300–330 | 562.0–612.9 | Dust storm season |
| 12 | 330–360 | 612.9–668.6 | Dust storm season ends |
Mars Date Converter Online
A free tool for converting dates between Earth and Mars. Converts an Earth date into a Mars Year, sol (Martian day), and areocentric solar longitude Ls — and back. Uses the same Allison & McEwen (2000) algorithm behind NASA’s official Mars24 calculator, with Mars Years numbered per R. Todd Clancy (Year 1 begins April 11, 1955).
Key concepts
Mars Sol Date (MSD)
A continuous count of Martian days (sols) from a reference epoch — the Mars equivalent of the Julian Date. One sol ≈ 24h 39m 35s.
MSD 52304 ≈ Feb 18, 2021
Solar Longitude (Ls)
The Mars-Sun angle from 0° to 360°, which defines the season independent of month length. Ls=0 is the Northern spring equinox, Ls=180 the autumn one.
Ls=90 → summer solstice
Mars Year (Clancy)
A continuous year count where Year 1 begins April 11, 1955 (Ls=0). One Mars year ≈ 668.6 sols ≈ 687 Earth days.
Curiosity landing: MY 31
When this is useful
- Finding the Mars date of NASA/ESA mission events (landings, milestones)
- Planning observations or scientific publications about Mars
- Calculating the Martian season for a given Earth date
- Studying astronomy and planetary science
- Creative projects: sci-fi, games, educational content about Mars
- Pure curiosity: "What’s the date on Mars right now?"
How to use it
- Choose a direction: "Earth → Mars" or "Mars → Earth"
- Enter the Earth date and time (UTC) — or click "Now"
- The result (year, sol, month, Ls) appears instantly
- For the reverse direction, enter a Mars Year and Ls to get the Earth date
Frequently asked questions
How accurate is this converter?
The tool uses the Allison & McEwen (2000) algorithm — the same one behind NASA’s official Mars24 calculator. Accuracy was checked against real mission landing dates: Curiosity (MY 31, Ls≈150.7°) and Perseverance (MY 36, Ls≈5.6°) — results match published figures exactly.
What is a "sol"?
A sol is a Martian solar day, the time it takes Mars to rotate once on its axis. It lasts 24 hours 39 minutes 35 seconds — slightly longer than an Earth day.
Why does the Mars Year start on April 11, 1955 specifically?
This is a reference epoch proposed by researcher R. Todd Clancy for continuous Mars Year numbering, now adopted by most of the scientific community. It doesn’t mark any special event on Mars that day — it’s simply a convenient starting point (the moment Ls equaled 0).
Why do Mars months vary so much in length (46 to 67 sols)?
Mars months aren’t defined by a fixed duration but as 30° intervals of solar longitude Ls. Because Mars’ orbit is elliptical, its orbital speed varies — so months vary in sols accordingly.
Is my input stored anywhere?
No. All calculations happen locally in your browser using JavaScript. Data is never sent to a server.