In tradition, the waxing Moon favours what you want to see grow, and the waning Moon favours what you want to see shrink. With hair it works like this:

• For the hair to grow back stronger, trim on the Waxing Moon.
• For the cut to last and the hair to take longer to grow back, cut on the Waning Moon.

The phase is the rule that governs. The sign the Moon is in that day is what separates a good day from a better one, and that is why the calendar below gives two lists for each goal.

The First Quarter Moon runs from the second day after the New Moon until the day before the Full Moon. Within it, the best days are the ones with the Moon in a water sign (Cancer, Scorpio and Pisces) or earth sign (Taurus, Virgo and Capricorn). These are the signs tradition calls fertile in farming, and the same logic passed from planting to hair.

In this case the idea is to trim little, just the ends, so the strand grows back stronger.

The Last Quarter Moon runs from the second day after the Full Moon until the day before the New Moon. Within it, the best days are the ones with the Moon in Aries or Sagittarius, fire signs: in tradition, a cut made with the Moon there takes longer to grow back.

Leo is also a fire sign, and even so it is left out. The cutting tradition sets apart two signs in which hair grows back faster, Leo and Virgo, and they are avoided during the Waning Moon. That is why the days that "also work" for the cut already come without them.

The calendar does not mark the day of the New Moon or the Full Moon, nor the day after each one. On those days the Moon is turning from one phase to the other, and the whole rule depends on knowing whether it is waxing or waning. These are the exact instants in the period, in Brasília time:

In October 2026, the New Moon is on the 10th, at 12:50pm, and the Full Moon on the 26th, at 1:12am; in November 2026, the New on the 9th, at 4:02am, and the Full on the 24th, at 11:54am; in December 2026, the New on the 8th, at 9:52pm, and the Full on the 23rd, at 10:28pm; in January 2027, the New on the 7th, at 5:25pm, and the Full on the 22nd, at 9:17am; in February 2027, the New on the 6th, at 12:56pm, and the Full on the 20th, at 8:24pm; and in March 2027, the New on the 8th, at 6:30am, and the Full on the 22nd, at 7:44am.

To trim and make your hair grow, every day below is a Waxing Moon day. When the Moon changes sign partway through the day, the time is written next to it.

In October 2026, the best days are 12 and 13 (Scorpio); 16 from 10am, 17 and 18 (Capricorn); and 21 from 9:40am, 22 and 23 until 4:55pm (Pisces), and 14, 15, 19, 20, 24 and 25 also work. In November 2026, the best are 13 and 14 (Capricorn); 18 and 19 (Pisces); and 22 and 23 (Taurus), and 11, 12, 15, 16, 17, 20 and 21 also work. In December 2026, the best are 10, 11 and 12 until 1:10pm (Capricorn); 15 and 16 (Pisces); and 20 and 21 until 7:30pm (Taurus), and 13, 14, 17, 18, 19 and 22 also work. In January 2027, the best are 11, 12 and 13 until 6:15pm (Pisces); 16 and 17 (Taurus); and 20 and 21 (Cancer), and 9, 10, 14, 15, 18 and 19 also work. In February 2027, the best are 8 and 9 (Pisces); 12, 13 and 14 until 1pm (Taurus); and 16 from 3:40pm, 17 and 18 until 4:35pm (Cancer), and 10, 11, 15 and 19 also work. In March 2027, the best are 11 from 1:20pm, 12 and 13 until 6:35pm (Taurus); 16 and 17 (Cancer); and 20 and 21 (Virgo), and 10, 14, 15, 18 and 19 also work.

For the cut to last longer, every day below is a Waning Moon day, and none of them has the Moon in Leo or Virgo during business hours.

In October 2026 there is no best day, because this month the Waning Moon does not pass through Aries or Sagittarius, and 1, 2, 3, 9, 28, 29, 30 and 31 work. In November 2026 there is none either, for the same reason, and 6, 7, 8, 26 and 27 work. In December 2026, the best day is 7, from 12:10pm (Sagittarius), and 3, 4, 5, 6, 30 and 31 also work. In January 2027, the best are 4 and 5 (Sagittarius) and 31 (Sagittarius), and 1, 2, 3, 6, 27, 28, 29 and 30 also work. In February 2027, the best are 1 and 2 until 12:35pm (Sagittarius) and 27 and 28 (Sagittarius), and 3, 4, 5, 23, 24, 25 and 26 also work. In March 2027, the best are 1 until 7:40pm (Sagittarius) and 27 and 28 (Sagittarius), and 2, 3, 4, 5, 6, 7, 24, 25, 26, 29, 30 and 31 also work.

October and November don't have a “best” day for a haircut, and the calendar is right about that: in these two months the Moon passes through Aries and Sagittarius while it's still waxing. If you want the cut to last and you're short on time, the days that “also work” already get the phase right, and that's the main rule.

To read the calendar, three notes:

• Brasília time. All times are given in the Brasília time zone, with no daylight saving. If you live in Amazonas, Rondônia, Roraima, Mato Grosso or Mato Grosso do Sul, subtract one hour; in Acre, two. This only changes anything on the days that come with a time attached.
• Business hours. The days were chosen looking at the window from 8am to 8pm, when a salon is open. A day with no time attached has the Moon in the same sign through that whole window.
• The phase is the rule; the sign is the refinement. If none of the best days fit your schedule, a day from those that “also work” is better than a day with the wrong phase.

This calendar answers the question “which day is the Moon good for a haircut?”, and that holds equally for everyone in the country. Electional astrology, which is the choice of a date, looks at more things at once:

• the time of day, because the sky changes hour by hour and the Moon can go out of bounds, which is the stretch where it makes no more aspects before changing sign;
• Venus, the planet of beauty and appearance, and its condition at that moment;
• the your city and your schedule: the sky is calculated for where you are, and the search stays within the period and hours you're free.

That's what the election Cut your hair does: it crosses the Moon's phase and sign with Venus and with your city, within the period you choose, and hands you the day and time. If your goal is the opposite, making your hair grow, there is also the election Grow your hair out.

And the questions that come up most on this subject, with the short answer: