Customized lunar phase calendar

Overview of tools for asteroid observers on this site

Source code for this service, and some pre-generated example calendars, are available.

This page will generate a calendar of lunar phases for a specified year, suitable for printing. I would suggest simply clicking "Generate calendar" to see what I mean by that, then hitting the browser back arrow and modifying the calendar to suit your needs. In particular, you may find that the 'landscape' version is a better fit to your wall.

Select a year and the events you want shown on the calendar, and click 'Generate calendar' to get a lunar calendar for that year. Years 1900 to 2100 are supported, though events will only be shown for the past few and next few years. I'll add further years as we get closer to them.

The calendar will print on two US letter or A4 pages. Snip one edge with scissors and assemble with transparent tape.

The language setting currently affects only the days of the week and the months. It wouldn't be difficult to extend that, at least to other European languages (PostScript is sadly ignorant of Unicode).

If you've questions or see problems, or would like to see this in your language, please contact me at p‮ôç.ötulpťcéjôřp@otúl‬m (modified to baffle spammers).

Reasoning behind these calendars

I do a fair bit of work writing software for asteroid observers ("planetary defense", the folks looking for rocks that might hit the earth). There's usually about a week or so around each full moon where we can't observe much, and a few days before/after that where moonlight interferes to an annoying extent. There aren't many people left whose schedules revolve around lunar phases, but we're among them.

Some Christmases back, my sister gave me a printed calendar vaguely resembling the ones shown here. It was useful, and had better artwork than what I'm providing here. It wasn't particularly oriented to what a working astronomer might actually need (it was a bit "New Age"-ish), but it made me think about what I'd actually want to have.

The column of days of the month was on the left edge. So it was easy to find the day of the month you wanted in January, but a little more difficult by the time you got to the end of the year. Putting it in the middle helped.

I added the 'Su Mo Tu...' to make it still easier to find the desired day (and so that you could find out that next Tuesday is the 17th, or vice versa), and made it possible to note holidays and such.

The lunar month names are the traditional ones from the Maine Farmer's Almanac (I'm from Maine). This is apparently an old English scheme, in which there are three month names per season :

Winter:
   After Yule
   Wolf
   Lenten

Spring:
   Egg
   Milk
   Flower

Summer:
   Hay
   Grain
   Fruit

Autumn:
   Harvest
   Hunter's
   Before Yule

There are slightly more than twelve lunar cycles per year. So every two or three years, you get four full moons in a season. In such a case, the third full moon is called a 'blue moon'. (The modern definition in which the second full moon in a Gregorian-calendar month is called 'blue' is much more recent.) The most recent blue moon was in August 2024; the next will be in May 2027.

This was discussed and analyzed in two articles in Sky & Telescope in May 1999 and in a follow-up article a few months later.

For quite similar reasons, the Chinese and Hebrew calendars (where the months follow the lunar cycle and the years follow the solar cycle) have a "thirteenth month", again every two or three years.