Moon Phase Calendar

What is a moon phase calendar?

A moon phase calendar is a month-by-month map of the lunar cycle. Instead of looking up one date at a time, you see every day of the month at once: which phase the Moon is in, how much of it is lit, and the exact moments the four quarter phases (new moon, first quarter, full moon, and last quarter) occur. It is the fastest way to answer questions like “when is the next full moon,” “what phase is the Moon in tonight,” or “was the Moon full on the day I was born.”

The calendar at the top of this page is a live lunar calendar, not a copied table. You pick any month and any year from 1900 to 2100, and the tool computes the phase for every single day from real lunar astronomy: the actual positions of the Sun and Moon on that date. Each day shows the phase name, a phase emoji, and the illuminated percentage. The four quarter instants of the month are found by numerical search and listed with their exact times in UTC, and any day that contains a quarter instant is highlighted with a gold border so it jumps out of the grid.

People use a phases of the moon calendar for many reasons. Gardeners plan planting around the new and full moons, photographers chase the full moon for night shots, anglers and hunters check the moon before a trip, and astrology students track the lunar cycle because traditional astrology reads the new moon as a time for beginnings and the full moon as a time of culmination. Whatever your reason, a moon calendar that computes its own numbers is more trustworthy than a static image, because you can check any date it shows and get the same answer twice.

This moon phase calendar is free, works entirely in your browser, and needs no account. Change the month or year and the grid redraws instantly. Use the Previous month and Next month buttons to step through time, Copy summary to take the whole month as plain text, or Print for a clean paper copy of the calendar and the quarter times.

How to use the calendar

1. Pick a month. Use the Month dropdown to choose any month of the year. The calendar redraws as soon as you change it.
2. Pick a year. Type any year from 1900 to 2100 into the Year field and press Enter or click outside the field. The tool validates the year and shows an error message if it is out of range, so you never get a silently wrong calendar.
3. Read the grid. Each day cell shows the date, the phase emoji, and the phase name. Hover over a day (or check its description) to see the exact illuminated percentage for 12:00 UTC that day. Days with a gold border contain a quarter instant.
4. Check the quarter instants. Below the grid, the “Phase instants this month” list gives the exact date and time of the new moon, first quarter, full moon, and last quarter, all in UTC.
5. Step through time. The Previous month and Next month buttons move one month back or forward, wrapping across years, so you can scan a whole season in seconds.
6. Save or print. Copy summary puts the full month, with every daily phase and the quarter times, on your clipboard as plain text. Print produces a clean black-on-white version of the calendar.

How it works

There is no moon phase table behind this tool. Every number is computed from the date you choose using the same kind of math astronomers use for approximate planetary positions.

The single quantity that decides the phase is the elongation: the angular separation between the Moon and the Sun as seen from Earth, measured along the ecliptic. At new moon the elongation is near 0 degrees, because the Moon sits between the Earth and the Sun. At full moon it is near 180 degrees, because the Moon is opposite the Sun. The tool computes the geocentric ecliptic longitudes of the Sun and the Moon for 12:00 UTC on each day, subtracts them, and that difference is the elongation.

The Sun and Moon positions come from a low-precision Keplerian orbital solution: each body’s orbital elements are evaluated for the day number, Kepler’s equation is solved by iteration to get the true position on the orbit, and for the Moon a set of perturbation terms is added to correct the simple ellipse. This is Paul Schlyter’s well-known method for computing planetary positions (https://stjarnhimlen.se/comp/ppcomp.html), and the implementation was cross-checked against published moon phase almanac values. Background on the lunar phase itself is covered clearly at https://en.wikipedia.org/wiki/Lunar_phase.

Once the elongation is known, the phase is read off from eight 45-degree bins centered on the quarter points: New Moon from 337.5 to 22.5 degrees, Waxing Crescent 22.5 to 67.5, First Quarter 67.5 to 112.5, Waxing Gibbous 112.5 to 157.5, Full Moon 157.5 to 202.5, Waning Gibbous 202.5 to 247.5, Last Quarter 247.5 to 292.5, and Waning Crescent 292.5 to 337.5 degrees. These are the standard eight phases of the lunar cycle, which repeats every 29.53 days from one new moon to the next.

The quarter instants need more than a daily sample, because the exact moment of a new or full moon usually falls between midnights. The tool scans the elongation in fine steps through the month to bracket each crossing of 0, 90, 180, and 270 degrees, then bisects on the elongation until the time is pinned down to 1-minute precision. The illumination percentage comes from the standard formula: illumination = (1 – cos(elongation)) / 2, which is 0 percent at new moon and 100 percent at full moon.

Two honest limits apply. First, all times are in UTC, not your local time: a new moon at 15:50 UTC happens at a different clock time wherever you live, so convert before planning around it. Second, the quarter times are computed, not copied from an almanac, and agree with published almanac values to within a few minutes. That is plenty for planning, photography, gardening, and astrology, but if you need second-level precision for scientific work, use a professional ephemeris.

Worked example

Here is a worked example with real computed values, so you can see exactly what the calendar does. Open the tool above and set it to October 2026.

The quarter finder returns four instants for the month, all in UTC: the Last Quarter on October 3 at 13:26 UTC, the New Moon on October 10 at 15:50 UTC, the First Quarter on October 18 at 16:12 UTC, and the Full Moon on October 26 at 04:19 UTC. These match published moon phase almanacs to within a few minutes: the new moon agrees to the minute, and the full moon is 7 minutes from the almanac value. In the grid, October 3, 10, 18, and 26 carry the gold border that marks quarter days.

The daily cells tell the story of the month. October 10 at 12:00 UTC shows the New Moon emoji with 0.0% illuminated, because the new moon instant falls later that same day. October 26 shows the Full Moon emoji with 99.9% illuminated. Between them, October 18 shows First Quarter at 48.3% illuminated, and on the waning side October 7 shows Waning Crescent at 11.2% illuminated as the Moon shrinks toward the October 10 new moon. Every value in this example was produced by the engine itself. If you open October 2026 in the calendar above, you will see the same numbers.

Frequently asked questions

What causes the phases of the Moon?

The phases are caused by the changing geometry of the Sun, Earth, and Moon as the Moon orbits the Earth. We always see the same lit half of the Moon, the half facing the Sun, but the angle we view it from changes through the month. At new moon the Moon sits between the Earth and the Sun, so its dark side faces us and it is invisible. At full moon the Moon is opposite the Sun, so its fully lit side faces us. The calendar above computes this geometry directly from the Sun-Moon angular separation, which astronomers call the elongation: near 0 degrees at new moon, near 180 degrees at full moon, and the eight named phases are 45-degree bins of that angle.

How accurate are the quarter times in this moon phase calendar?

The quarter instants are found by bisection on the computed Sun-Moon elongation to 1-minute precision, and they agree with published moon phase almanacs to within a few minutes. For October 2026 the engine’s new moon matches the almanac to the minute and the full moon is 7 minutes off. That level of accuracy is plenty for planning a night out, timing photography, gardening by the moon, or astrology work. If you need second-level precision for scientific or navigation purposes, use a professional ephemeris instead of any web calendar.

Why are the quarter times shown in UTC?

UTC is the single unambiguous reference time, so the same instant reads the same for everyone on the calendar. A new moon at 15:50 UTC is 11:50 AM Eastern Time, 4:50 PM in London in winter, and 8:50 PM in Karachi, so convert the UTC time to your own timezone before planning around it. The daily phases and illumination percentages are likewise computed for 12:00 UTC each day, which keeps every day of the month on one consistent clock.

Can I look up moon phases for other years, past or future?

Yes. The calendar accepts any month and any year from 1900 to 2100, and every date is computed live from orbital mechanics rather than looked up in a stored table, so past and future months work exactly the same way. Leap years are handled correctly: February 2024 shows 29 days, while February 2025 shows 28. Use the Previous month and Next month buttons to step through time one month at a time, or jump straight to a date with the month and year controls.

How is this different from other moon phase apps and calendars?

Most moon phase pages show a static image or a precomputed table that only covers a fixed range of dates. This calendar computes every value itself: the Sun and Moon positions from Keplerian orbital elements with lunar perturbation corrections, the eight phases from the elongation angle, the illumination from the standard (1 – cos(elongation)) / 2 formula, and the quarter instants by numerical bisection. Because nothing is looked up, any date from 1900 to 2100 works, the method is documented in the open, and you can verify any number it shows.

Is this moon phase calendar free? Do I need an account?

Yes, it is completely free, and no account or signup is needed. The calculation runs entirely in your browser: your dates never leave your device, nothing is sent to a server, and nothing is stored. Use the Copy summary button to take a whole month as plain text, or the Print button for a clean black-on-white paper copy of the calendar and quarter times.

Related tools

• Birth date moon phase calculator: find the exact moon phase and illumination for any birth date.
• Moon phase on my birthday: what the Moon looked like on the day you were born, with the phase name and emoji.
• What time is sunrise today: accurate sunrise times computed from real solar astronomy for any date.
• What time does the sun set: sunset times for any date, from the same verified solar engine.
• Lunar calculators: browse every ZodiaScope Moon calculator in one place.
• All astrology calculators: browse the complete ZodiaScope calculator collection.
• Today’s moon phase: tonight’s moon phase, illumination, moon age, and distance, updated daily.

About the author

This moon phase calendar was built by the ZodiaScope editorial team. We publish astronomy-accurate astrology tools: every phase in the calendar is computed live from orbital mechanics, not looked up in a table, and the methods are documented so the results can be checked. Our interpretations follow traditional astrology and are offered for reflection and entertainment.

Published: October 16, 2026. Last updated: October 16, 2026.