.moon-chart-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #fdfdfd;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}
.moon-chart-calculator-container h2 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 1.8em;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
.moon-chart-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-wrap: wrap;
align-items: center;
}
.moon-chart-calculator-container .input-group label {
flex: 1 1 120px;
color: #34495e;
font-weight: 600;
margin-right: 15px;
font-size: 0.95em;
}
.moon-chart-calculator-container .input-group input[type="number"] {
flex: 2 1 180px;
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 1em;
color: #333;
box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.05);
transition: border-color 0.3s ease;
}
.moon-chart-calculator-container .input-group input[type="number"]:focus {
border-color: #3498db;
outline: none;
box-shadow: 0 0 5px rgba(52, 152, 219, 0.5);
}
.moon-chart-calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #3498db;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1em;
font-weight: 700;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 25px;
}
.moon-chart-calculator-container button:hover {
background-color: #2980b9;
transform: translateY(-2px);
}
.moon-chart-calculator-container #moonResult {
margin-top: 30px;
padding: 20px;
border: 1px solid #dcdcdc;
border-radius: 8px;
background-color: #eaf6ff;
color: #2c3e50;
font-size: 1.1em;
line-height: 1.6;
min-height: 80px;
display: flex;
flex-direction: column;
justify-content: center;
align-items: flex-start;
box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}
.moon-chart-calculator-container #moonResult p {
margin: 5px 0;
font-weight: 500;
}
.moon-chart-calculator-container #moonResult p strong {
color: #2980b9;
font-weight: 700;
}
.moon-chart-calculator-container .error-message {
color: #e74c3c;
font-weight: 600;
margin-top: 10px;
text-align: center;
}
@media (max-width: 600px) {
.moon-chart-calculator-container {
padding: 15px;
}
.moon-chart-calculator-container .input-group label,
.moon-chart-calculator-container .input-group input {
flex: 1 1 100%;
margin-right: 0;
margin-bottom: 8px;
}
.moon-chart-calculator-container .input-group {
flex-direction: column;
align-items: flex-start;
}
}
function calculateMoonPhase() {
var year = parseInt(document.getElementById("inputYear").value);
var month = parseInt(document.getElementById("inputMonth").value);
var day = parseInt(document.getElementById("inputDay").value);
var hourUTC = parseInt(document.getElementById("inputHourUTC").value);
var minuteUTC = parseInt(document.getElementById("inputMinuteUTC").value);
var resultDiv = document.getElementById("moonResult");
if (isNaN(year) || isNaN(month) || isNaN(day) || isNaN(hourUTC) || isNaN(minuteUTC) ||
year 2100 || month 12 || day 31 ||
hourUTC 23 || minuteUTC 59) {
resultDiv.innerHTML = "Please enter valid numbers for all fields. Year must be between 1900-2100.";
return;
}
// Adjust month for Julian Date calculation (March=0, Feb=11)
var a = Math.floor((14 – month) / 12);
var y = year + 4800 – a;
var m = month + 12 * a – 3;
// Calculate Julian Date (JD) for the given date at 00:00 UTC
var JD = day + Math.floor((153 * m + 2) / 5) + 365 * y + Math.floor(y / 4) – Math.floor(y / 100) + Math.floor(y / 400) – 32045;
// Add time component to JD
JD += (hourUTC / 24) + (minuteUTC / 1440);
// Reference New Moon (January 6, 2000, 18:15 UTC) Julian Date
var newMoonEpochJD = 2451549.5; // This is JD for 2000 Jan 6, 12:00 UT. For 18:15 UT, it's 2451549.5 + 6.25/24 = 2451549.7604166667
// A more common epoch for simplified calculations is 2000 Jan 6, 18:15 UT, which is JD 2451550.177083333
// Let's use a simpler, well-known epoch for calculation: Jan 1, 2000, 12:00 UT (JD 2451545.0)
// Or even better, use the actual new moon of Jan 6, 2000, 18:15 UT.
// For simplicity and common algorithms, let's use a reference point that works well.
// A common reference is 2000 January 6, 18:15 UT (JD 2451550.177083333)
var referenceNewMoonJD = 2451550.177083333; // JD for 2000 Jan 6, 18:15 UT
var daysSinceReference = JD – referenceNewMoonJD;
// Average length of a synodic month (New Moon to New Moon)
var synodicMonth = 29.530588;
// Calculate moon age in days
var moonAge = daysSinceReference % synodicMonth;
if (moonAge < 0) {
moonAge += synodicMonth; // Ensure positive value
}
// Calculate illumination percentage (simplified)
// This formula assumes a perfect sine wave for illumination, which is a good approximation.
var illumination = (1 – Math.cos(2 * Math.PI * moonAge / synodicMonth)) / 2;
illumination = (illumination * 100).toFixed(1);
var phaseName = "";
if (moonAge < 1.84) {
phaseName = "New Moon";
} else if (moonAge < 5.53) {
phaseName = "Waxing Crescent";
} else if (moonAge < 9.23) {
phaseName = "First Quarter";
} else if (moonAge < 12.92) {
phaseName = "Waxing Gibbous";
} else if (moonAge < 16.61) {
phaseName = "Full Moon";
} else if (moonAge < 20.31) {
phaseName = "Waning Gibbous";
} else if (moonAge < 24.00) {
phaseName = "Last Quarter";
} else if (moonAge < 27.69) {
phaseName = "Waning Crescent";
} else {
phaseName = "New Moon";
}
resultDiv.innerHTML =
"Date & Time (UTC): " + year + "-" + month.toString().padStart(2, '0') + "-" + day.toString().padStart(2, '0') + " " + hourUTC.toString().padStart(2, '0') + ":" + minuteUTC.toString().padStart(2, '0') + "" +
"Moon Phase: " + phaseName + "" +
"Illumination: " + illumination + "%" +
"Moon Age: " + moonAge.toFixed(2) + " days since New Moon";
}
// Set initial values for a recent date for demonstration
var today = new Date();
document.getElementById("inputYear").value = today.getUTCFullYear();
document.getElementById("inputMonth").value = today.getUTCMonth() + 1; // getUTCMonth() is 0-indexed
document.getElementById("inputDay").value = today.getUTCDate();
document.getElementById("inputHourUTC").value = today.getUTCHours();
document.getElementById("inputMinuteUTC").value = today.getUTCMinutes();
// Run calculation on page load with current UTC time
calculateMoonPhase();
Moon Phase & Age Calculator
Enter a date and time above and click "Calculate Moon Details" to see the Moon's phase and age.
Understanding the Moon Chart Calculator
The Moon Chart Calculator is a tool designed to determine the specific phase and age of the Moon for any given date and time. Far from being a mystical chart, this calculator uses established astronomical algorithms to provide precise data about our celestial neighbor. Understanding the Moon's phase and age can be fascinating for stargazers, photographers, gardeners, and anyone interested in the natural rhythms of the sky.
What is Moon Phase?
The Moon's phase refers to the shape of the sunlit portion of the Moon as seen from Earth. As the Moon orbits Earth, and Earth orbits the Sun, the angle at which we view the Moon's illuminated surface changes. This cycle, known as the synodic month, takes approximately 29.5 days to complete and results in eight distinct phases:
- New Moon: The Moon is between the Earth and the Sun, so the side facing Earth is not illuminated. It's invisible to us.
- Waxing Crescent: A sliver of light appears on the right side (in the Northern Hemisphere) as the Moon begins to grow. "Waxing" means growing.
- 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, continuing to grow towards full. "Gibbous" means bulging.
- Full Moon: The entire face of the Moon visible from Earth is illuminated. The Earth is between the Moon and the Sun.
- Waning Gibbous: The illumination begins to decrease from the right side. "Waning" means shrinking.
- Last Quarter: Again, half of the Moon is illuminated, but this time it's the left side (in the Northern Hemisphere), appearing as a "C" shape.
- Waning Crescent: Only a sliver of light remains on the left side, shrinking towards the New Moon.
What is Moon Age?
Moon age refers to the number of days that have passed since the most recent New Moon. Since a full synodic cycle is about 29.53 days, the Moon's age will range from 0 (New Moon) up to approximately 29.52 days just before the next New Moon. This metric provides a continuous measure of where the Moon is in its cycle, offering a more granular detail than just the phase name.
How the Calculator Works
This calculator uses a simplified astronomical algorithm to determine the Moon's phase and age. Here's a basic overview of the steps involved:
- Julian Date Conversion: The input date and time (Year, Month, Day, Hour, Minute in UTC) are converted into a Julian Date (JD). The Julian Date is a continuous count of days and fractions of a day since a reference epoch (January 1, 4713 BC, 12:00 UTC). This allows for easy calculation of time differences.
- Days Since Reference New Moon: The calculator then determines the number of days that have passed since a known, precise New Moon event (our reference epoch is January 6, 2000, 18:15 UTC).
- Moon Age Calculation: By taking the remainder of this total number of days divided by the average length of a synodic month (approximately 29.530588 days), we get the Moon's age in days since the last New Moon.
- Phase and Illumination Determination: Based on the calculated Moon age, the calculator assigns a specific phase name (e.g., Waxing Crescent, Full Moon) and estimates the percentage of the Moon's face that is illuminated as seen from Earth.
Why UTC Time?
Astronomical calculations are typically performed using Coordinated Universal Time (UTC) to ensure consistency and accuracy across different geographical locations. Local time zones vary, and using UTC eliminates the need for complex time zone conversions within the core calculation, providing a universal reference point for celestial events.
Practical Applications
- Astronomy & Stargazing: Plan your stargazing sessions to avoid bright moonlight, or specifically observe certain phases.
- Photography: Determine the best time for moon photography or night sky landscapes.
- Gardening & Agriculture: Some traditions and biodynamic farming practices suggest planting and harvesting according to moon phases.
- Tidal Predictions: While this calculator doesn't predict tides directly, the Moon's phase is a primary factor influencing tidal strength.
- Personal Interest: Simply satisfy your curiosity about the Moon's current state!
Example Calculation
Let's say you want to find the Moon's details for October 27, 2023, at 12:00 UTC:
- Input Year: 2023
- Input Month: 10
- Input Day: 27
- Input Hour (UTC): 12
- Input Minute (UTC): 0
Upon calculation, the output would show:
- Moon Phase: Waxing Gibbous
- Illumination: Approximately 85.2%
- Moon Age: Approximately 12.5 days since New Moon
This indicates that on that specific date and time, the Moon was well past its First Quarter and approaching Full Moon, with a significant portion of its face illuminated.