Mars calendar Year 39 begins September 30

September 30, 2026, marks the beginning of Year 39 on Mars. While Earth uses the Gregorian calendar, scientists use a specific system for Mars to facilitate data comparisons and study Martian climate.

The current Mars year system was first described in a scientific paper by Todd Clancy of the Space Science Institute in 2000. The system uses the planet's orbit around the sun, with each Martian year lasting approximately 687 Earth days.

The count for Mars years began with Year 1 on April 11, 1955, coinciding with the northern spring equinox. Although the starting date was described as “arbitrary,” the significant dust storm of 1956 serves as a notable marker within the early years of the calendar.