Mars sol converter

The sols around today, with the moment each Perseverance sol begins in your time zone and the matching Curiosity sol. Each new sol starts about 40 minutes later on the clock than the one before.

Each rover keeps its own sol count. The day it lands is sol 0, and the count ticks over at local mean midnight at the landing site — mean solar time, not the true Sun, so every sol is exactly 24 h 39 m 35.244 s long. That's different from the Mars Sol Date, a planet-wide count kept at the prime meridian (Airy-0), much as Earth has both local dates and the Julian Date.

Because the two rovers are about 60° of longitude apart, their sols start roughly four hours apart on the clock, so for a few hours each sol the two missions are on "different days" of the same Martian week.

A sol is 2.75% longer than an Earth day, so sol starts creep later on our clock by about 40 minutes a day. Roughly every 36 Earth days the start slips past midnight and jumps a whole calendar date — that day sees no sol begin at all. Mission planners noticed early: in the first months of a mission, when teams live on Mars time, their "morning" shift walks all the way round the clock in just over a month.

For scale: Spirit and Opportunity, which landed in January 2004, were each designed for a 90-sol mission. Spirit kept talking until sol 2,210 in 2010; Opportunity was heard from for over 5,100 sols, until a planet-wide dust storm in June 2018. Curiosity has now passed 5,000 sols.