# Martian orbital cycle and calendar

> Developing situation record from CLSTR: https://clstr.news/situations/martian-orbital-cycle-and-calendar
> Updated: 2026-10-02T09:43:06.000Z. Sources: 4. Developments: 2.

On September 30, 2026, Mars entered Year 39 of its current calendar system. This timekeeping method, first described by Todd Clancy in 2000, uses the planet’s orbit around the sun to facilitate scientific data comparison and climate studies.

The new Martian year begins at the northern vernal equinox, marking the start of spring in the northern hemisphere and autumn in the southern hemisphere. Each Martian year lasts approximately 687 Earth days. 

Due to the planet’s elliptical orbit, seasonal durations vary. As Mars approaches the sun during the second half of its year, the atmosphere warms and winds increase surface dust. Temperatures on the planet fluctuate from 0 to 60 degrees Celsius in the summer to as low as -110 degrees Celsius in the winter.

## Timeline

### 2026-10-02: Mars begins new orbital cycle around the sun

Mars has begun a new 687-day orbit around the sun, marking the Martian New Year at the northern vernal equinox.

2 sources. https://clstr.news/cluster/mars-begins-new-orbital-cycle-around-the-sun

### 2026-09-30: Mars calendar Year 39 begins September 30

September 30, 2026, marks the start of Year 39 on Mars, following a scientific timekeeping system used to study the planet's climate and facilitate data comparisons.

2 sources. https://clstr.news/cluster/mars-calendar-year-39-begins-september-30

---
Cite as: Martian orbital cycle and calendar. CLSTR, https://clstr.news/situations/martian-orbital-cycle-and-calendar