I'm not entirely sure why, but at some point I got it in my head to make up a calendar for Mars. The problem is that seconds and minutes don't add up to an even Martian day.
So I made up analogs to those units and gave them Latinesque names. Or maybe I looked up Latin equivalents. I can't remember, I wrote the initial version of this in 2006.
The initial conversion is from seconds to a punctum. All the other conversions up to months/lunes keep the same ratios as on Earth, so the net effect would be like if you had a clock that was running 2% slow.
- Punctum
- 1.0274875 seconds
- Minorum
- 60 puncta, 61.64925 seconds
- Horum
- 60 minora
- Sol
- 24 hora
- Lune
- 37 sols (38 if lune number is divisible by 9)
- Anno
- 18 lunes, 668 sols
Leap years wound up being a bit more complicated because the fraction isn't nicely close to ¼ like here. I added an end-of-year leap day on annos where division by 5 leaves a remainder of 0, 2 or 4, and the anno is not divisible by 50.
For sol names I stuck with mythology. For lune names I tried to pick things that were relevant to Mars. When I ran out of ideas I picked landers (yes, only the American ones -- I make no apologies) and then people who were important to space and science in general.
Sols:
- Heliosol
- Deimosol
- Phobosol
- Terrasol
- Aphrodisol
- Zeusol
- Cronosol
Lunes:
- Percival
- Asaph
- Giovanni
- Wells
- Burroughs
- Mariner
- Viking
- Sojourner
- Odyssey
- Spirit
- Phoenix
- Sagan
- Bradbury
- Gagarin
- Shepard
- Armstrong
- Tereshkova
- Ride
Here are some dates I decided to convert. I'm not sure why I set the zero point to 1795 BCE any more, I know I wanted to always have positive dates and going that far back all but guaranteed that. I'm just not sure why I picked that particular point.
Edit, 12 Oct 2026: While browsing through old blog posts, I found my answer in May of 2006:
A not-so-quick back-of-the-envelope calculation places the Martian north winter solstice on the same day as January 1 way back in 1754 BCE, assuming my guess about when the Martian solstices happen is at all accurate. That became the first day of the first month of Martian Year 0.
So there we have it: I made the winter solstice be New Year's Day, and it aligned with our New Year's Day way back during the Bronze Age. I'm not sure when 1754 BCE became 1795, and I have no interest in finding out. I'm hoping I just mistyped it twenty years ago.
Today's date (Earth): ----, ---- --, ---- --:--:--
Mars date: ----, ---- --, ---- --:--:--
E-mail format: ---, -- --- ---- --:--:--
---- -- --M--:--:-- = +---- -- --T--:--:-- (Current date)
---- -- --M--:--:-- = –1794-01-01T00:00:00Z (Martian Year Zero, Jan 1, 1795 BCE)
2000-01-01M00:00:00 = +---- -- --T--:--:-- (Mars Y2K)
---- -- --M--:--:-- = +1969-07-16T13:32:00Z (Apollo 11 Launch)
---- -- --M--:--:-- = +1969-07-20T20:18:00Z (Apollo 11 Landing)
---- -- --M--:--:-- = +2000-01-01T00:00:00Z (Earth Y2K)
---- -- --M--:--:-- = +---- -- --T--:--:-- (Leap day example, Mars → Earth conversion)
---- -- --M--:--:-- = +2016-07-20T00:00:00Z (Leap day example, Earth → Mars conversion)
