Detailed guide
How to use the moon-phase calculator
The four primary lunar phases
At new moon, the Moon is approximately in the Sun’s direction from Earth and is largely invisible at night. The illuminated portion grows toward first quarter, reaches full moon when Earth lies more nearly between Sun and Moon, and decreases again through last quarter.
The table gives the astronomical instant of each primary phase. Waxing and waning intermediate phases occur between these events but do not appear as separate rows.
Why local date and time can differ
A lunar phase is one global astronomical moment, yet that instant can fall on different local calendar dates in different time zones. The page uses Europe/Berlin unless the application is configured with another zone.
The service applies astronomical approximations based on Jean Meeus, converts ephemeris time to UTC and then to local time. This is suitable for calendar planning; high-precision scientific work should use specialist ephemerides.
Practical uses for moon-phase dates
Lunar phases help with sky observation, night photography, events and cultural calendars. Nights around new moon are darker without strong moonlight, while full moon brightens the night. Cloud and local light pollution remain important practical factors.
This calendar does not assess broad medical, psychological or gardening claims associated with lunar phases. It provides astronomical dates, not medical or agricultural advice.