What was the Moon phase when you were born?

How is my birth Moon phase calculated?

To find the Moon phase at birth, we first convert your recorded local time to a universal instant using your birth city's time zone. We then calculate the Sun and Moon positions from the ephemeris and measure the angle between them. Near 0° is new Moon, near 90° first quarter, near 180° full Moon, and near 270° last quarter. The intervals between them form the waxing and waning crescent and gibbous phases.

Phases do not fall on fixed calendar dates: the roughly 29.5-day cycle does not line up with calendar months. You cannot find your birth phase just from the day of the month. That is why the form asks for your date, time and city. With a known time we can also display an approximate illuminated fraction beside the phase.

That percentage is an estimate derived from the ephemeris Sun–Moon longitude difference, not a measurement from a photograph and not a forecast. It describes the geometry of the lit face visible from Earth. NASA's account of the eight phases explains the same changing view of sunlight on the Moon.

Source: NASA Science — Moon Phases

What if I do not know my birth time?

If your birth hour is unknown, we do not guess one. We calculate both 00:00 and 23:59 in the selected city's local date. If both are in the same phase, we give that phase; if the day crosses a boundary, we show both candidates. We withhold an exact illumination percentage because a few hours can matter near a boundary.

If you see two possibilities, look for the time on a family record, birth certificate or hospital record. An approximate time should not be treated as certain at a boundary. If historical time-zone data is unavailable on your device, the calculator may use a longitude-based approximation, which can also affect an edge case.

What can a birth phase tell you?

Astrological tradition uses new Moon as a symbol for beginnings, waxing Moon for development, full Moon for visibility, and waning Moon for completion and review. This is a symbolic vocabulary, not a personality test. A phase does not determine who you are, the outcome of a relationship or what will happen to you. It works best as a theme to reflect on.

If you want your Moon sign, use the separate calculator: it finds the Moon's zodiac sign, not the Sun–Moon angle. For today's phase and the astronomy of the cycle, read the moon-phases guide. A full birth chart puts these pieces alongside the Sun, Moon and other placements in a broader context.