Cosmic Birthday
When's your next birthday — on every planet?
Each planet has its own year. Each year has its own birthday. Here's the next date a new Mercury / Mars / Saturn year starts for you.
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How we find each date
Your age on a planet is your age in days divided by that planet's orbital period. The next whole planetary year completes at birth + (floor(age_on_planet) + 1) × orbital_period. We convert that back into an Earth date.
Mercury birthdays come around every 88 days — so if you haven't had one this quarter, you're overdue. Pluto is the rarest: most humans get exactly one.
Why celebrate?
Every excuse to celebrate is a good one. Put your next Mars birthday on your calendar — it's unlikely any of your friends have ever marked one.
Related
- Age on Other Planets — how old are you on each one.
- Life in Weeks — all your Earth birthdays, visualized.