Example 1
- Date: 1990-05-15
Aquarius (Air)
L ≈ 303.8° → the integer part of (303.8/30)=10 → Aquarius.
Moon sign calculator
Pick a date. The calculator computes the Moon’s mean ecliptic longitude at UTC noon and splits it into 12 signs of 30°. 15 May 1990 is about 303.8° and Aquarius. 1 January 2000, near the J2000 epoch, is Scorpio. A sketch, not a full sky position.
A mean-longitude sketch, not a reading. Phase: moon phase. Sun: zodiac sign. Article: Moon sign.
Result
Pick a date to see the approximate Moon sign.
How it works
A tropical Moon sign is the sign the Moon sits in. A full result needs an ephemeris. Here you only get mean longitude: days d from J2000.0 (UTC noon on 1 January 2000), then L ≈ 218.3164477 + 13.17639648 × d. Sign = the integer part of ((L mod 360) / 30), Aries through Pisces.
15 May 1990: L ≈ 303.8°, index 10, Aquarius and Air. 1 January 2000: L ≈ 218.3°, Scorpio. 8 August 1988: L ≈ 85°, Gemini. 7 July 1977: L ≈ 0.6°, Aries. 13 April 2013 about 57°, Taurus. 16 June 1994 about 176°, Virgo.
This is mean longitude, not the equation of the center, nodes, or parallax. On a sign boundary the result can disagree with an ephemeris by a full sign. It is not a scientific forecast and not a timed birth chart.
Do not mix it with moon phase (disc lighting) or the Sun sign (day and month). The element beside the result is the sign’s element, as on the zodiac-element page. The model uses UTC noon, with no time zone and no longitude.
One field: date as YYYY-MM-DD. Click Calculate. Mean motion in this sketch is about 13° per day, so the next day shifts L by that constant.
Treat the result as an ecliptic 12×30° exercise. Do not read it as a fortune, a personality grade, or a day’s instructions.
Formula
d = JD(UTC noon of date) - 2451545.0
L = 218.3164477 + 13.17639648 × d (degrees; then L mod 360)
index = the integer part of (L / 30) mod 12 → Aries...Pisces
Educational approximation. Not a lunar ephemeris.
How to use
- Pick the date in the date field, YYYY-MM-DD. The model uses UTC noon on that date.
- Click Calculate. The result is the sign from L mod 360 divided by 30°.
- Check 15 May 1990: L ≈ 303.8°, Aquarius and Air.
- Near the epoch, open 1 January 2000: L ≈ 218.3°, Scorpio.
- Compare moon phase and Sun sign for the same date. Those are different layers.
Mean lunar longitude at noon UTC
15 May 1990 gives L ≈ 303.8° and Aquarius. Mean longitude at noon UTC, not an ephemeris and not a science forecast.
- Aquarius
- The sign from L ≈ 303.8° on 15 May 1990. A mean, not a professional-ephemeris position.
- Moon
- A noon-UTC model. Local hour and zone do not enter. A sign sketch, not a horoscope.
Suggested uses
- Learn the ecliptic split into twelve 30° signs.
- Compare several dates and the Moon’s ~13°/day mean motion.
- Workshop: mean longitude vs a full ephemeris (error talk).
- Practice the integer part of ((L mod 360)/30) on concrete numbers.
- Pair with Sun sign and moon phase.
- Get a repeatable result without planetary software.
Examples
Example 2
- Date: 2000-01-01
Scorpio (Water)
L ≈ 218.3° → Scorpio (near the J2000 epoch).
Example 3
- Date: 1988-08-08
Gemini (Air)
L ≈ 85° → Gemini.
Example 4
- Date: 1977-07-07
Aries (Fire)
L ≈ 0.6° → Aries.
Example 5
- Date: 2013-04-13
Taurus (Earth)
L ≈ 57° → Taurus.
Example 6
- Date: 1994-06-16
Virgo (Earth)
L ≈ 176.1° → Virgo.
Related calculators
Frequently asked questions
What Moon sign is 15 May 1990?
Aquarius and Air. L ≈ 303.8°, the integer part of (303.8/30) = 10 counting from Aries.
What about 1 January 2000?
Scorpio. L ≈ 218.3°, near the J2000.0 epoch the formula starts from.
Is this a scientific forecast?
No. It is mean longitude without corrections. On a boundary an ephemeris can show another sign.
Does clock time change the result?
Not in this calculator. We take UTC noon on the chosen date. A birth-chart Moon needs an exact time.
How is this different from moon phase?
Phase is how much of the disc is lit in the synodic cycle. Here the sign comes from ecliptic longitude.
How is this different from the Sun sign?
The Sun sign uses day and month. This Moon-sign sketch uses L and moves about every two and a half days.
What about 8 August 1988 and 7 July 1977?
1988-08-08: L ≈ 85°, Gemini. 1977-07-07: L ≈ 0.6°, Aries.
Why about 13° per day?
The constant 13.17639648° is mean motion in this model. Not a full orbit with accelerations.
Does time zone enter?
No. UTC noon, no geographic longitude. Fine for a class exercise; not for a chart.
Does a blank date yield epoch Scorpio?
No. Without a date there is no L. Pick a day on the calendar.
Knowledge sources
The phase in this calculator follows the Moon cycle. NASA describes the same cycle; a horoscope is not in the formula.
Page updated in 2026.