A moon phase is really an angle.

The Moon produces no light of its own; it reflects the Sun's. It is always a sphere with one lit half and one dark half — the only thing that changes is how much of the lit half we can see from Earth. That is decided by the positions of the Sun, Earth and Moon relative to one another.

In both astronomy and astrology the phase reduces to a single number: the angular distance between the Sun and the Moon. When they share a longitude — an angle of 0° — the Moon's lit face points entirely away from us and it vanishes from the sky. That is the new Moon. At 90° we see half of it: the first quarter. At 180° the Moon stands opposite us with its lit face fully turned our way — the full Moon. Then the same path runs backwards.

This is what makes phases computable to the minute. Baby Astro derives the eight phases — new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter and balsamic crescent — from ephemeris data for the current instant, and reports the illumination percentage and the Moon's age in days alongside. None of it is read off a calendar.

Calendars assign the full Moon to a day, but a full Moon is really an instant: the second at which the Sun–Moon angle reaches exactly 180°. Before it the Moon is still waxing; after it, it begins to wane. Saying "today is a full Moon" means that instant fell on that day — and because of time zones, that can slide by a day depending on where you are.

The same applies to the new Moon, which is why one source saying "full Moon on Tuesday" and another saying Wednesday need not be a mistake; they may simply be using different time zones. Baby Astro computes the phase for the real instant on your device, so what you see corresponds to the sky where you actually are.

The synodic month — new Moon to new Moon — averages 29.5 days. Because calendar months run 30 or 31, the phases drift backwards a little each month. Occasionally two full Moons fit inside one calendar month; the second is popularly called a blue Moon. It has nothing to do with colour and is purely an accident of counting.

Most moon content covers one layer and conflates two separate things. Where the Moon is takes two independent facts to describe: where it sits in the cycle (the phase), and which sign it occupies. They move at different speeds and say different things.

The phase is a rhythm of about 29.5 days, traditionally read as an arc: begin at the new Moon, sustain as it waxes, see clearly and culminate at the full, then release and finish as it wanes. The Moon's sign changes far faster — it spends roughly two and a half days in each — and sets the mood of the particular day.

Baby Astro's daily do/avoid suggestion comes from that second layer: the element of the sign the Moon is in. A Moon in a fire sign and a Moon in a water sign produce different suggestions for the same day, even at an identical phase. We say so explicitly because the common mistake is to attribute those suggestions to the phase — which is not how the app works.

The meaning tradition attaches to the phase cycle is a suggested rhythm: set intentions and begin at the new Moon, push forward as it waxes, see results at the full, then simplify and close as it wanes. Plenty of people find that useful, and much of the usefulness comes from having a regular review rhythm at all — stopping once a month to look at what you started and what needs finishing is a good habit regardless of where it came from.

Let us also be clear about what it is not. There is no reliable evidence that the full Moon disrupts sleep, increases births or changes human behaviour. Those beliefs are widespread, have been tested repeatedly, and no consistent effect has been found. Moon phases offer a framework for timing, not a cause.

If you are looking for rituals and practices, those have their own page. This one is the mechanism; that one is what people do with it. And the same line holds on both: the app makes no guarantees about the future, gives no medical or psychological advice, and declines requests for spells and the like.