Article
Moon phase
Pick a date. The card ages the Moon from the reference new moon on 6 January 2000, 18:14 UTC, and names the phase. 25 March 2024 is full moon, about 100%, age 14.6 days. 15 May 1990 is waning gibbous, 72.9%. Simplified calendar astronomy, not a reading.
The Moon phase calculator does this. It is entertainment and a tradition lesson, not a reading and not life advice.
The idea in brief
Pick a date. The card ages the Moon from the reference new moon on 6 January 2000, 18:14 UTC, and names the phase. 25 March 2024 is full moon, about 100%, age 14.6 days. 15 May 1990 is waning gibbous, 72.9%. Simplified calendar astronomy, not a reading.
You want the moon phase on a given day. This card computes the disk age from the new moon of 6 January 2000, 18:14 UTC, and names the phase. It is a calendar, not a horoscope.
A calendar phase, not a horoscope
Many pages tie the Moon phase to mood, sleep, sowing, and “the energy of the day”. A full moon then gets an almost magical status. Calendar astronomy is smaller: it asks how much of the disk is lit.
Here Moon age runs from the new moon on 6 January 2000, 18:14 UTC, in a 29.53058867-day period. 25 March 2024 is a full moon, about 100%. 15 May 1990 is a waning gibbous, 72.9%. That is not a weather forecast and not a balcony reading.
Words on this page
The short forms below belong to this card only. Another page with a similar name may compute a different rule.
- reference new moon
- 6 January 2000, 18:14 UTC. Moon age is counted from there.
- 29.53058867
- The synodic period in days in this model.
- illumination percent
- The share of the disk the formula treats as bright. Full moon is about 100%.
What Moon age means on this card
Age is days since the reference new moon, not "how old the Moon is". Near 0 is new, near 7 first quarter, near 14 full, near 22 last quarter.
Illumination percent follows the same age. 100% does not mean you must do something. It means the disk is almost fully bright in this model.
When this helps
| Situation | What the card shows |
|---|---|
| What moon phase is 25 March 2024? | Full moon, about 100% lit, age about 14.6 days from the reference new moon. |
| You want new moon or full moon on a calendar, not a reading. | 6 January 2000 is the reference new moon. 15 May 1990 is a waning gibbous, 72.9%. |
| You compare with an astronomy app. | A minute-level ephemeris can sit a fraction of a day away. Here is a simplification from one start new moon. |
How to read it
Full moon, about 100%, age 14.6 days. Mid-cycle in this model.
2000-01-06 is new moon, 0.7%, age 28.8 days. 1990-05-15 is waning gibbous, 72.9%, age 19.9 days.
Example from the card
From the new moon to 25 March 2024
Start: 6 January 2000, 18:14 UTC. You count the Moon's age in days and name the phase. 25 March 2024 lands near 14.6 days, a full moon. 15 May 1990 is a waning gibbous.
Typical numbers from the card
| Question from the card | This card's answer |
|---|---|
| What phase is 25 March 2024? | Full moon, about 100%, age 14.6 days. Mid-cycle in this model. |
| What about 6 January 2000 and 15 May 1990? | 2000-01-06 is new moon, 0.7%, age 28.8 days. 1990-05-15 is waning gibbous, 72.9%, age 19.9 days. |
| Is this a horoscope? | No. It is simplified calendar astronomy. It does not predict weather or a day’s fate. |
Typical mistakes
| Mistake | What goes wrong | How to avoid it |
|---|---|---|
| You read the phase as a daily horoscope. | The disk name is not advice for a decision. | Leave "when to sow" and "when to marry" outside the card. |
| You type a clock time because the full moon "fell in the evening". | The field is a date. The new-moon minute does not enter beyond the fixed UTC start. | Check age in days, not a birth clock. |
| You mix the phase with the Moon sign. | Phase is how much of the disk is lit. The Moon sign is another card and a mean longitude. | Do not mix a full moon with Aquarius. |
Before you treat the result as a reading
- You know where the age starts: new moon 6 January 2000, 18:14 UTC.
- 25 March 2024 can be checked as a full moon.
- The percent is illumination, not "reading strength".
- This is not a minute ephemeris and not a horoscope.
Frequently asked questions
What phase is 25 March 2024?
Full moon, about 100%, age 14.6 days. Mid-cycle in this model.
What about 6 January 2000 and 15 May 1990?
2000-01-06 is new moon, 0.7%, age 28.8 days. 1990-05-15 is waning gibbous, 72.9%, age 19.9 days.
Is this a horoscope?
No. It is simplified calendar astronomy. It does not predict weather or a day’s fate.
Where does lunar age come from?
From the day difference versus the 6 January 2000, 18:14 UTC new moon, modulo 29.53058867 days.
Is the result as tight as an ephemeris?
It is a UTC sketch. Professional tables can be tighter on hour and location.
What does illumination percent mean?
The share of the disc that looks lit in this formula. Full moon ≈ 100%, new moon ≈ 0%.