Martian Calendar

Apps

Prohowich Martian Calendar

The complete Mars calendar — MY −0199 to MY 1500 — built for accuracy, not fiction.

In development

Prohowich Martian Calendar converts any Earth date to its precise Mars equivalent using the Mars Solar Date (MSD) system — no guessing, no approximation.

What It Does

  • Shows the current Mars date, time (AMT), and sol count in real time
  • Browse any Mars Year from MY −0199 to MY 1500
  • 24-month Martian calendar with fixed month lengths per century, recalculated each century to account for Mars orbital precession
  • Season tracking: Northern and Southern hemisphere views
  • Lₛ×15° milestone table — every orbital checkpoint with AMT time
  • Full year view with orbital events: equinoxes, solstices, Aphelion, Perihelion
  • Earth↔Mars time converter
  • Complete Mars Year table with MNYD, MSD, sol counts, and all seasonal markers
  • Three day-of-week naming systems: Earth, Numerical (Greek ordinals), Mars Planetary

The Calendar System

Month lengths are fixed within each Martian Century (~100 Mars years, ~188 Earth years), then recalculated for the next century using actual Lₛ crossing times. Every Lₛ×15° milestone is guaranteed to fall within its correct month. Regular years = 668 sols; augmented (leap) years = 669 sols, with the extra sol added to Month 24.

The Icon

38χ marks when the app became viable — Mars Year 0038, Month 22 (Χ: Charmē). The background is Mars. The ring shows all 24 months by season color, sized by sols per month.

At a Glance

  • Real-time Mars clock — Current AMT updated live
  • MY −0199 → MY 1500 — 1,700 Mars years of coverage
  • 24 named months — Greek letters + etymology
  • Season-aware — Switch N/S hemisphere instantly
  • Orbital events — Equinoxes, solstices, Aphelion, Perihelion
  • Time converter — Earth UTC ↔ Mars AMT (also as a widget)

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