Moon calendar

UmbraLux calculates every date and time on this page itself, with the astronomy library astronomy-engine – the same calculation the UmbraLux app uses for its charts. As usual in astrology, positions are measured in the tropical zodiac: the signs start at the vernal equinox and span 30° each.

New moon, first quarter, full moon and last quarter are the moments when the Moon stands 0°, 90°, 180° or 270° east of the Sun, measured by the apparent positions of Sun and Moon – as the astronomical almanacs define them. The Moon changes sign when it crosses into the next zodiac sign, about every two and a half days.

An automated test compares our times for 2026 and 2027 with published values: all 99 moon phases lie within one minute of NASA JPL Horizons, and it checks them against the US Naval Observatory's tables too. The 24 moon sign changes it checks (one a month) lie within one minute of JPL Horizons.

A moon calendar shows two things: the moon phase, how much of the Moon is lit (from new moon through the first quarter to full moon and back through the last quarter), and the moon sign, the zodiac sign the Moon is in. The Moon runs through its phases in about 29.5 days and through all twelve signs in about 27.3 days, so the full moon falls in a different sign every month.

In German-speaking countries the moon calendar is also a tradition for house, garden and body care, made popular above all by the German book "Vom richtigen Zeitpunkt" ("The right moment") by Johanna Paungger and Thomas Poppe. By this tradition every moon sign and phase has its favourable activities. We describe the tradition and calculate the dates for it.