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Printable moon phase calendar for any month

Pick a month and print a moon calendar at the exact size of the paper in your tray. Every disc is drawn from that day's computed illuminated fraction, so a thin crescent and a fat one have different shapes. The sheet is drawn as vector geometry in your browser, with no watermarks or sign-ups, and nothing is uploaded.

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Sheet— Days— Full moon— New moon—

How this generator works

For each day, the sheet works out what fraction of the Moon's disc is lit at 12:00 UTC (noon). That number comes from the positions of the Sun and Moon computed with the standard Meeus series, corrected for the difference between clock time and the uniform time the series is written in. The gap is roughly 75 seconds today, enough to move the Moon about 41 arcseconds. New moon, first quarter, full moon and last quarter are computed as exact instants, and a day carries one of those names only when the instant falls within that UTC day. The readout lists the days of the month that hold a full moon and a new moon.

The drawing uses that number directly. The lit region of each disc is bounded by a semicircle on one side and a semi-ellipse on the other, and the ellipse's width is set by the day's illuminated fraction: it is widest at new and full moon and collapses to a straight line at exactly half. So the inked area equals the fraction times the area of the disc, and this site's test suite measures that on the emitted drawing. Waxing moons are lit on the right, which is the northern-hemisphere view. The sheet's footer says so, because the picture is mirrored south of the equator. Choose "Drawn phases with phase names" to print the phase name under each day that holds a new moon, first quarter, full moon or last quarter, or tick "Print percent lit" to print each day's lit percentage, rounded to a whole number, under its disc.

A phase is a moment and a calendar cell is a day, so a moon calendar has to choose a time zone before it can say "the full moon is on the 4th". This one uses UTC days and prints its basis in the footer. Percent-lit labels and phase names print only when the cells are tall enough to hold them without running into the row below, so a landscape sheet with six week rows leaves them off. The range is 1800 to 2150; toward the far end the slowing of Earth's rotation is an estimate, and published sources already differ by minutes about the year 2100, though the calendar day is not in doubt.

Frequently asked questions

How accurate are the phases on this sheet?
The engine's phase instants agree with the US Naval Observatory's published table to under a minute and a half across every era where Earth's rotation has been measured. The phase of each day is computed from the positions of the Sun and Moon using the standard Meeus series, with the Espenak and Meeus correction for the slowing of Earth's rotation. It does not use the common shortcut of counting days since a known new moon and dividing by 29.53, which drifts by up to about fourteen hours and names the wrong day several times a year.
Why does my sheet show a full moon on a different day than another calendar?
Almost always the time zone. A phase happens at one instant, and a full moon at 00:40 UTC on the 5th is still the evening of the 4th in New York. This sheet puts each phase on the UTC date its instant falls on and draws every disc as lit at 12:00 UTC, and the footer prints that basis, so you can tell which convention produced the sheet. For the phase at a specific local moment, you need the exact phase time, which a wall calendar does not print.
Can I print a blank moon calendar for tracking the moon myself?
Yes. Set Style to "Blank circles to fill in" and every day gets an empty circle to draw in. Science teachers use this version for a month-long observation exercise, where each student draws the moon they see. The dates, weekday columns and week rows are still computed for the month you picked, the percent-lit labels are left off, and the footer reads "Blank tracking sheet: draw what you observe."
Which years can it generate, and why is the disc shape different from other calendars?
Any month from 1800 to 2150, the range the underlying astronomy is trusted over. Past about 2050 the exact clock times of phases are less certain, because the slowing of Earth's rotation is measured as it happens and cannot be predicted exactly, but the calendar day stays right. The disc shape differs because most printables pick one of eight stock glyphs, so every crescent looks the same. Here the terminator is an ellipse whose width comes from that day's illuminated fraction, so a 3 percent crescent and a 47 percent crescent have visibly different shapes.
Is anything uploaded or stored?
No. The sheet is generated as vector geometry inside this page, printed through your browser's own dialog, and exists only on your device. There is no account, no watermark and no stored setting: close the tab and the sheet is gone.

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