Blue poster lunar calendar

These silver and blue posters (which I've been producing since 1989) show the phase of the moon for each night of the year, screenprinted with silvery metallic ink on a deep midnight blue background. As well as dates and days of the week, the calendar gives the exact times of the full, new and quarter moons, and the times when the moon changes from one sign of the zodiac to the next. The posters measure 12 inches by 32 inches (30cm x 80cm) (approx.), and are both lovely and useful!
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The date and time of the Sun's movement into each zodiac sign is printed at the bottom of the calendar - these, of course, include the solstices and equinoxes (in March, June, September and December) - and a key to the zodiac symbols is also given. When there's a solar or lunar eclipse, the type of eclipse and time of greatest eclipse are shown instead of the full- or new-moon time, this being just a few minutes different. The moon's phases are drawn for midnight, and the last one shown in each month (for 24:00 GMT on the last day) is pictured again at the top of the next month's column.

All the times shown on the calendar are in Greenwich Mean Time. It's a 'Northern-hemisphere' design, in the sense that the shapes would be back-to-front (or upside-down!) in the Southern hemisphere - though in any case the moon is usually seen with the bright limb turned downwards, toward the horizon, the exact angle depending both on your latitude and on the time of night. The calendar is nevertheless useable anywhere in the world, since the moon's shape appears (almost exactly) the same wherever you are on Earth.

A Southern-hemisphere version is also available, however (pictured right), which shows all the shapes the other way up, and uses New-Zealand standard time-zone (12 hours East of Greenwich).

Many traditional festivals are scheduled using the phases of the moon, or a combination of the lunar and solar cycles. The Chinese New Year, for example, is celebrated on a new moon - almost always the second new moon after the winter solstice. Easter Sunday is the first Sunday on or after the first full moon after the spring equinox.

The average time from one full moon to the next is 29.5306 days (a 'synodic month'), which is about one day less than the average calendar month, and this is why the pattern on the calendar slopes upwards to the right. This pattern continues if you put calendars for successive years side-by-side.

The moon always moves forwards through the zodiac (unlike the planets, which sometimes appear to go backwards, or retrograde, against the background of the 'fixed stars'). She spends a bit more than two whole days in each zodiac sign, completing the cycle through all 12 signs in one 'tropical month' of on average, 27.3216 days. The time when the moon moves into a zodiac sign from the previous one - an 'ingress' - is shown on the calendar by the Zodiac symbol of the new sign, with the time printed next to it, using the 24-hour clock.

The calendar uses the usual 'tropical zodiac', in which the Sun moves into Aries on the Spring equinox each year. Some people (biodynamic gardeners for example) are interested in the sidereal zodiac, which corresponds instead to the constellations of stars seen in the sky. The tropical and sidereal zodiacs coincided in AD 221 (allegedly), but due to the precession of the equinoxes, the tropical zodiac has moved backwards relative to the sidereal one by nearly 25 degrees. The moon thus moves into any particular sidereal sign about 1 day and 21 hours after moving into the same tropical sign (the one shown on the calendar).

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