Current Moon
Sun Today (UTC)
About the Astronomy Calendar
This tool provides a comprehensive overview of celestial events visible from Earth. Moon phases are calculated using Conway's algorithm (accurate to within 1 day). Sun rise and set times use a simplified NOAA algorithm referenced to UTC. Astronomical events include major meteor showers, solar and lunar eclipses, planetary conjunctions, and seasonal markers (equinoxes and solstices).
Moon Phase Reference
- New Moon: Moon is between Earth and Sun; not visible
- Waxing Crescent: Less than half lit, growing (right side in Northern Hemisphere)
- First Quarter: Right half illuminated
- Waxing Gibbous: More than half lit, growing
- Full Moon: Earth between Sun and Moon; fully visible
- Waning Gibbous: More than half lit, shrinking
- Last Quarter: Left half illuminated
- Waning Crescent: Less than half lit, shrinking
Frequently Asked Questions
How accurate are the moon phase calculations?
Conway's algorithm provides accuracy of ±1 day, which is sufficient for most observational purposes. The exact moment of a phase (e.g., "Full Moon at 14:35 UTC") requires more complex calculations and may differ by up to 2 hours. For mission-critical astronomy work, consult a dedicated ephemeris.
Why are sun rise/set times in UTC?
UTC (Coordinated Universal Time) is used as a universal reference. To convert to your local time, add or subtract your timezone offset. For example, New York (EST = UTC-5) sees sunrise 5 hours earlier than the UTC time. Use the dedicated Sunrise Sunset Calculator for city-specific times.
What is a "moon age"?
Moon age is the number of days since the last New Moon. A new synodic month (full cycle from New Moon to New Moon) takes 29.53 days. Knowing moon age helps predict tides, animal behavior, and optimal stargazing conditions (less moonlight during New Moon week).
How often is the events list updated?
The events list is hardcoded with verified dates for major astronomical events through 2027. We update it periodically as new events are confirmed by NASA and the International Astronomical Union.
Can I see past dates?
Yes! The moon phase and sun time calculations work for any date. Use the date controls in the calendar tab to browse historical or future months. Past astronomical events are not shown in the events tab, but you can check moon phase for any past date.