Where the numbers come from
Planetary positions, moon phases, signs, retrograde periods, and the aspects between planets are calculated on our servers with Astronomy Engine, an open-source astronomy library. We make reasonable efforts to check our results against published reference data, such as NASA/JPL Horizons.
Calculations are not perfect
We try to be accurate, but we do not guarantee that any position, time, or date is exact or error-free. Small differences from other almanacs, apps, and astrologers are normal and can come from:
- different calculation methods, models, and rounding;
- different definitions of events such as a station, a sign change, or when an aspect is exact;
- very short event times, where a difference of a minute or two can move an event across midnight.
Time zones and dates
Astronomical events happen at a single moment worldwide, but the calendar date depends on where you are. The lunar calendar shows event times in your device's time zone. Our weekly emails and some forecast views use UTC, so an event can fall on a different date than the one you see locally. Moon illumination for a calendar day is measured at 12:00 UTC on that date.
Birth details and personalized reports
Personalized forecasts and birth chart reports depend entirely on what you enter. If your birth time is missing or wrong, parts of a chart that depend on the time, such as the rising sign and houses, can be off or left out. When you type a birth place, we look it up with a free geocoding service and use the best match. It can pick the wrong city, and we cannot confirm historical time zone or daylight saving rules for every place and year. Check the place and time zone shown on your account, and correct them if needed.
Interpretation is separate
These calculations describe where bodies appear in the sky. What they mean for you is astrology, which is interpretation and not science. See the Astrology Disclaimer.
Please tell us about errors
If you think something on the site is wrong, contact us with the page and what you expected to see. We will take a look.