Time is weird. We think of a year as this fixed, universal constant, but it's really just a measurement of how long one specific rock takes to loop around a single star. If you moved to the next rock over, everything you know about schedules, aging, and seasons would basically fall apart. So, how long is the year on Mars? It's long. Like, 687 Earth days long.
That’s nearly double what we’re used to here on Earth. If you lived on Mars, you'd have to wait almost two Earth years just to blow out your birthday candles. It sounds simple on paper, but when you look at the mechanics of orbital mechanics and the way NASA engineers actually have to live while managing rovers like Perseverance or Curiosity, the reality is a lot more complicated than a simple number.
The math behind the Martian orbit
Mars sits further out in the solar system than we do. Because it's the fourth planet from the Sun, it has a much larger circle to complete. Simple physics, right? But it isn't just about the distance. Mars also moves slower. While Earth zips along its orbit at about 30 kilometers per second, Mars drags its feet at roughly 24 kilometers per second.
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When you combine a larger "track" with a slower "runner," you get a massive inflation of time. To be precise, a Martian year is 686.98 Earth days. If you want to get technical—and NASA scientists always do—that translates to 1.88 Earth years.
Why we talk about Sols instead of days
Here is where things get genuinely annoying for anyone trying to sync a watch. A "day" on Mars isn't 24 hours. It’s 24 hours, 39 minutes, and 35 seconds. Astronomers call this a Sol.
Because a Sol is slightly longer than an Earth day, the calendar year on Mars doesn't just neatly divide into 687 days. If you count in Martian Sols, the year is actually about 668.6 Sols long. This creates a nightmare for timekeeping. Imagine your clock drifting by 40 minutes every single day. Within a few weeks, your "noon" is happening in the middle of the night.
NASA teams working on missions like the InSight lander or the Zhurong rover often have to live on "Mars time." They wear special watches and shift their entire lives by 40 minutes every day. Eventually, they’re eating breakfast at 3 AM and heading to sleep when the sun comes up in California, all because the Martian year and day refuse to play nice with Earth’s rhythm.
Seasons on Mars: A long, cold slog
Since the Martian year is nearly twice as long as ours, the seasons are stretched out too. But they aren't equal. Earth has a pretty circular orbit, so our seasons are roughly the same length. Mars? Not so much.
Mars has a very "eccentric" orbit. It’s more of an oval than a circle.
When Mars is closest to the sun (perihelion), it moves faster. When it’s furthest away (aphelion), it slows down. This means the seasons in the northern and southern hemispheres of Mars have wildly different durations. For example, spring in the northern hemisphere lasts about 194 Sols, while autumn is a much shorter 142 Sols.
- Spring (North): 194 Sols
- Summer (North): 178 Sols
- Autumn (North): 142 Sols
- Winter (North): 154 Sols
And "summer" on Mars isn't exactly a beach trip. Even at the equator during the height of the warm season, temperatures might hit 70°F ($21°C$) during the day, but they’ll plummet to -100°F ($-73°C$) at night. The length of the year means these brutal winters last for months on end, which is a massive problem for solar-powered tech. The Opportunity rover famously "died" because a global dust storm—which happens more frequently during certain parts of the long Martian year—blocked out the sun for too long, and the rover couldn't stay warm.
The "Leap Year" problem on the Red Planet
We use leap years on Earth because our year is roughly 365.25 days. Every four years, we add a day to catch up. On Mars, the math is even messier. Since a year is 668.6 Sols, you can’t just have a standard calendar.
In the late 1980s, a scientist named Thomas Gangale proposed the Darian calendar. It’s one of the most popular "fan-made" systems for future Mars colonists. In this system, there are 24 months. Most months have 27 or 28 Sols. To keep the calendar in sync with the orbit, you have to add leap Sols in a complex pattern—specifically, six leap years every decade.
It’s a lot to keep track of. Honestly, it makes you realize how lucky we are that Earth’s rotation and orbit are relatively stable.
How the long year affects human exploration
If we ever send humans to Mars, the 687-day year becomes a survival bottleneck. You can't just leave whenever you want. Because Earth and Mars move at different speeds, they only "align" once every 26 months. This is called an opposition.
Space agencies have to wait for these launch windows to open. If you miss your ride home, you aren't just waiting a few months; you’re stuck on Mars for another two years until the planets align again. This dictates everything from how much food a crew needs to the psychological toll of being millions of miles away from home.
The long Martian year also means more exposure to radiation. On Earth, our magnetic field and atmosphere protect us. On Mars, you're out there in the open. Spending two years on the surface—because that's how long a standard "stay" would be based on orbital cycles—means engineers have to build habitats that can withstand 687 days of constant cosmic ray bombardment.
The misconception about "Mars Years"
People often ask, "How old would I be on Mars?"
It's a fun thought experiment, but it's where people usually get the math wrong. They just divide their age by two. If you're 30 on Earth, you aren't exactly 15 on Mars; you're more like 16. This happens because the ratio is $1:1.88$.
But biologically, nothing changes. Your cells don't care that the planet moved slower. You'd still be aging at the same rate, you'd just have fewer birthdays to celebrate. For future colonists, this might actually be a weird psychological benefit. Having a "year" take twice as long might make life feel slower, even if the daily grind is exactly the same.
Dust Storm Season
One of the most dramatic parts of the Martian year is the dust storm cycle. Every year, as Mars approaches the sun, the atmosphere heats up. This causes massive temperature swings that kick up dust. Sometimes, these storms stay local. Other times, they become "global dust events" that shroud the entire planet in a hazy, red gloom for weeks.
If you were living there, you’d have to track the "year" not just for your calendar, but for your safety. Knowing when the "dusty season" is coming is the difference between keeping your life-support systems running and having your solar panels rendered useless by a layer of grime.
Making the transition to Martian time
If you're planning on keeping track of the Martian year, you need to think in terms of Solar Longitude ($L_s$). This is how astronomers actually measure where Mars is in its orbit.
- $L_s = 0$: This is the vernal equinox (start of northern spring).
- $L_s = 90$: Northern summer solstice.
- $L_s = 180$: Autumnal equinox.
- $L_s = 270$: Northern winter solstice.
Instead of saying "it's October on Mars," scientists say "we're at $L_s 200$." It’s less poetic, but it’s the only way to be accurate when the "year" is so stretched out.
The sheer scale of the Martian year is a reminder of how hostile and different space really is. We are tuned to a 24-hour day and a 365-day year. Our bodies, our sleep cycles, and our cultures are built on that rhythm. Mars throws all of that out the window.
To prep for a future on the Red Planet, the first thing we have to do is learn to live slower. We have to accept that a year is a marathon, not a sprint.
If you want to track where Mars is right now, check out the NASA Mars Clock (often called "Mars24"). It’s a tool developed by the Goddard Institute for Space Studies that shows the current Sol and time for various landing sites. You can actually see the "drift" between Earth time and Mars time in real-time. It’s the best way to wrap your head around just how long that 687-day journey really feels.
Check your "Mars Age" using an online calculator to see how many Martian birthdays you've actually had. It’s a quick way to realize that on the fourth planet, we’re all a lot younger than we think.