About CycleCalcs
CycleCalcs is the home for celestial cycles: a free astronomy site built around one idea, that the sky runs on rhythms you can compute, watch, and learn. It began as a few fast calculators and grew into a full observatory bench: a live planetarium Sky Map, a Today in the Sky dashboard, an Eclipse Explorer, a Planet Parade Tracker, a pilotable flythrough of the solar system, a sorted reference of all 65 astronomical cycles, and a growing library of interactive lessons.
How the site works
Every position, phase, eclipse and rise time on CycleCalcs is computed live in your own browser by the open-source, MIT-licensed Astronomy Engine, the same class of model that serious sky software uses. Nothing is looked up from a fixed table, and nothing is computed on a server: there are no accounts, no tracking, and the pages work the same for everyone. Positions are accurate to well under a degree, and the planetary models are reliable for roughly the years 1700 to 2200. The methodology page documents the models, sources and accuracy limits behind every tool.
What we care about
Real astronomy, plainly explained. The site covers what the sky actually does: why the Moon waxes and wanes, why eclipses come in seasons, why planets gather in parades, how the equinoxes drift over 25,920 years. Where a topic has folklore attached, the pages say clearly what is established science, what is history, and what is neither.
No astrology, no forecasts. CycleCalcs computes where things are, not what they mean for your life. Planetary line-ups do not affect events on Earth, and no tool here suggests otherwise. The one numerology calculator is presented for what it is: a classical interpretive tradition with a long history, not science.
Honesty about limits. When a view is illustrative rather than measured (an enlarged planet, an artistic asteroid belt), the page says so. When a value is a long-term average or a contested estimate, the page says that too. Corrections are welcome and acted on.
Free to use, free to share
Everything on the site is free, supported by unobtrusive advertising and a few clearly disclosed affiliate links on the gear page. You can also put the sky on your own site with the free embeddable widgets: a live moon phase card, a next-eclipse countdown, and a planet parade tracker.
Privacy in one paragraph
The astronomy runs entirely on your device. The only network lookup any tool makes is optional geocoding when you ask for it: choosing "use my location" or typing a place name sends coordinates or your search text to a free geocoding service once, to name the spot or find it on the map. Preferences like your theme or saved location live in your own browser's storage, never on our servers. The full detail is in the Privacy Policy.
A note on accuracy
The tools aim to be correct and transparent, but they are provided for general educational and research use. They are not professional financial, investment, legal, or astrological advice. Orbital periods use standard mean values unless a page states otherwise.
Questions, corrections or ideas? Email info@cyclecalcs.com. If you spot a number that looks wrong, please say which page and what you expected; those are the best emails we get.