Check the moon phase for a date

The job

Planning a moonlit shoot or a dark-sky night means knowing where the moon is in its cycle on a given date. The calculator gives the moon's age in days, the named phase, the illuminated fraction, and how far the next full and new moons are.

How to do it

Pick the date and run it. The result card shows the phase name (new moon through waning crescent), the age counting from the last new moon, and the illumination as a percentage.

• Age 0 is a new moon; about 14.8 is full; the cycle repeats every ~29.53 days.
• Days to the next full/new moon help you pick the nearest matching date.

Worked example

A date with age ~15 and illumination ~100% is a full moon — the classic bright disk for night photos. Age ~0–2 is effectively moonless and best for seeing faint stars.

Limits

The estimate counts mean lunations from a reference new moon in January 2000, for dates in 1900–2100. Because the real orbit is elliptical, the true phase can lead or lag by up to roughly a day; for telescope-precise timing use an ephemeris. Rise and set times are not shown.