Sun Moon Calculator

Sun & Moon Phase Calculator

Enter a date and time to discover the Moon's phase and the Sun's zodiac sign for that moment.

Understanding the Sun & Moon

The Sun and Moon have captivated humanity for millennia, influencing everything from tides and agriculture to cultural beliefs and personal horoscopes. While the Sun dictates our seasons and daily rhythms, the Moon cycles through distinct phases, each carrying its own unique energy and appearance.

Moon Phases Explained

The Moon's phases are a result of the changing angles at which we view the Moon's illuminated surface as it orbits the Earth. The cycle, known as a synodic month, lasts approximately 29.5 days. This calculator uses a simplified astronomical model to determine the phase and illumination for your specified date and time (UTC).

  • New Moon: The Moon is between the Earth and Sun, so the side facing us is not illuminated. It's invisible in the night sky.
  • Waxing Crescent: A sliver of light appears on the right side (in the Northern Hemisphere) as the Moon begins to grow.
  • First Quarter: Half of the Moon is illuminated, appearing as a "D" shape. It's about a quarter of the way through its cycle.
  • Waxing Gibbous: More than half of the Moon is illuminated, growing towards fullness.
  • Full Moon: The entire face of the Moon is illuminated, appearing as a bright, complete circle. It's opposite the Sun in the sky.
  • Waning Gibbous: The illumination begins to decrease from the right side, moving towards the last quarter.
  • Last Quarter (or Third Quarter): Again, half of the Moon is illuminated, but this time the left side. It appears as a backward "D".
  • Waning Crescent: Only a sliver of light remains on the left side, shrinking towards the new moon.

This calculator provides the moon phase and its illumination percentage for any given date and time, offering a glimpse into the lunar cycle at that specific moment.

The Sun's Zodiac Sign

In Western astrology, the Sun's zodiac sign is determined by the position of the Sun against the backdrop of the twelve zodiac constellations at the time of a person's birth or any given date. Each sign is associated with specific personality traits and influences. The Sun spends approximately one month in each sign, moving through the entire zodiac over the course of a year.

This calculator will tell you which zodiac sign the Sun was in for your chosen date, providing a fun astrological insight.

How to Use the Calculator

  1. Enter the desired Year, Month, Day, Hour (in 24-hour format), and Minute into the respective fields. Please note that the time inputs are expected in Coordinated Universal Time (UTC) for consistent astronomical calculations.
  2. Click the "Calculate" button.
  3. The Moon's phase, its illumination percentage, and the Sun's zodiac sign for your specified date and time will be displayed below.

Example Calculation

Let's say you want to know the moon phase and sun sign for July 20, 1969, at 20:17 (8:17 PM) UTC, the approximate time of the Apollo 11 moon landing.

  • Year: 1969
  • Month: 7
  • Day: 20
  • Hour: 20
  • Minute: 17

Upon calculation, you would find that the Moon was in a Waning Crescent phase, approximately 18.0% illuminated, and the Sun was in Cancer.

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margin-left: 20px; margin-bottom: 15px; color: #666; } .calculator-article li { margin-bottom: 5px; } @media (max-width: 600px) { .calculator-form { grid-template-columns: 1fr; } .calculator-form button { grid-column: span 1; } } function calculateSunMoon() { var year = parseInt(document.getElementById("inputYear").value); var month = parseInt(document.getElementById("inputMonth").value); var day = parseInt(document.getElementById("inputDay").value); var hour = parseInt(document.getElementById("inputHour").value); var minute = parseInt(document.getElementById("inputMinute").value); var resultDiv = document.getElementById("sunMoonResult"); resultDiv.innerHTML = ""; // Clear previous results // Input validation if (isNaN(year) || isNaN(month) || isNaN(day) || isNaN(hour) || isNaN(minute)) { resultDiv.innerHTML = "Please enter valid numbers for all fields."; return; } // Basic range validation for date/time components if (year 2100 || month 12 || day 31 || hour 23 || minute 59) { resultDiv.innerHTML = "Please ensure all values are within a realistic range (e.g., Year 1900-2100, Month 1-12, Day 1-31, Hour 0-23, Minute 0-59)."; return; } // Create a Date object (UTC for consistency in astronomical calculations) // Note: JavaScript months are 0-indexed, so subtract 1 from input month. var inputDate = new Date(Date.UTC(year, month – 1, day, hour, minute, 0)); // Validate if the date itself is valid (e.g., Feb 30) if (inputDate.getUTCFullYear() !== year || inputDate.getUTCMonth() !== (month – 1) || inputDate.getUTCDate() !== day) { resultDiv.innerHTML = "The date entered is not a valid calendar date."; return; } // — Calculate Moon Phase — // Reference New Moon: Jan 6, 2000, 18:14 UTC (Julian Date 2451549.25972) // Synodic month: 29.530588 days var referenceNewMoon = new Date(Date.UTC(2000, 0, 6, 18, 14, 0)); // Month 0 is January var millisecondsPerDay = 1000 * 60 * 60 * 24; var daysSinceReference = (inputDate.getTime() – referenceNewMoon.getTime()) / millisecondsPerDay; var synodicMonth = 29.530588; var phaseFraction = (daysSinceReference / synodicMonth) % 1; if (phaseFraction < 0) { phaseFraction += 1; // Ensure positive fraction } var phaseDays = phaseFraction * synodicMonth; var moonPhaseName = ""; var illumination = 0; // Approximate phase boundaries and illumination calculation if (phaseDays < 1.84566) { // New Moon to early Waxing Crescent moonPhaseName = "New Moon"; illumination = Math.max(0, Math.min(5, (phaseDays / 1.84566) * 5)); } else if (phaseDays < 5.53699) { // Waxing Crescent moonPhaseName = "Waxing Crescent"; illumination = Math.max(5, Math.min(50, 5 + (phaseDays – 1.84566) / (5.53699 – 1.84566) * 45)); } else if (phaseDays < 9.22831) { // First Quarter moonPhaseName = "First Quarter"; illumination = Math.max(45, Math.min(55, 45 + (phaseDays – 5.53699) / (9.22831 – 5.53699) * 10)); } else if (phaseDays < 12.91963) { // Waxing Gibbous moonPhaseName = "Waxing Gibbous"; illumination = Math.max(50, Math.min(95, 50 + (phaseDays – 9.22831) / (12.91963 – 9.22831) * 45)); } else if (phaseDays < 16.61096) { // Full Moon to early Waning Gibbous moonPhaseName = "Full Moon"; illumination = Math.max(95, Math.min(100, 95 + (phaseDays – 12.91963) / (16.61096 – 12.91963) * 5)); } else if (phaseDays < 20.30228) { // Waning Gibbous moonPhaseName = "Waning Gibbous"; illumination = Math.max(50, Math.min(95, 95 – (phaseDays – 16.61096) / (20.30228 – 16.61096) * 45)); } else if (phaseDays = 21) || (currentMonth == 4 && currentDay = 20) || (currentMonth == 5 && currentDay = 21) || (currentMonth == 6 && currentDay = 21) || (currentMonth == 7 && currentDay = 23) || (currentMonth == 8 && currentDay = 23) || (currentMonth == 9 && currentDay = 23) || (currentMonth == 10 && currentDay = 23) || (currentMonth == 11 && currentDay = 22) || (currentMonth == 12 && currentDay = 22) || (currentMonth == 1 && currentDay = 20) || (currentMonth == 2 && currentDay = 19) || (currentMonth == 3 && currentDay <= 20)) { sunZodiacSign = "Pisces"; } // Display results resultDiv.innerHTML = "For " + month + "/" + day + "/" + year + " " + String(hour).padStart(2, '0') + ":" + String(minute).padStart(2, '0') + " UTC:" + "Moon Phase: " + moonPhaseName + "" + "Moon Illumination: " + illumination.toFixed(1) + "%" + "Sun's Zodiac Sign: " + sunZodiacSign + ""; }

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