Moon Phase Birthday

The Moon on the day you were born

Your birth Moon phase is a real astronomical fact: on the day you were born the Moon was at a particular angle to the Sun, somewhere in the 29.5-day cycle from new to full and back. This page computes it from the ephemeris rather than approximating it from a table.

The astrological reading of birth phase is less widely used than sign or house placements but has a long history, and it has one attractive property: it is a genuinely continuous variable rather than a twelvefold category, so it divides people differently from everything else in a chart.

What the eight phases are traditionally read as

• New — beginnings, instinct, acting before the whole picture is available.
• Waxing crescent — pushing against inherited circumstances; effort against friction.
• First quarter — crisis of action; people who need something to push against.
• Waxing gibbous — refinement, analysis, the urge to get it right before showing anyone.
• Full — awareness and relationship; things become visible, including to other people.
• Waning gibbous — communicating what has been learned; the teaching phase.
• Last quarter — crisis of consciousness; dismantling what no longer holds.
• Waning crescent — completion and release; a strong sense of an ending being carried.

Your lunar return

The Moon returns to the same phase roughly every 29.5 days, and to the same phase and the same zodiac sign roughly once a year — but not on your birthday. The offset between the solar year and the lunar cycle means your birth phase recurs on a date that drifts by about eleven days each year.

Every nineteen years, though, they realign almost exactly: the Metonic cycle. Your 19th, 38th and 57th birthdays fall on nearly the same Moon phase as the day you were born, usually within a few hours. That is a real astronomical coincidence, not an astrological claim, and it is one of the more satisfying things in this whole subject.

What you need

A birth date is enough for the phase. Adding a time and city refines the degree and pins the phase precisely if you were born within a few hours of an exact new, quarter or full Moon. Everything runs in your browser and nothing is stored.