alogic0/paskha.html

## paskha.html
<!DOCTYPE html>
<html>
<head>
  <title>Orthodox Easter Calculator</title>
</head>
<body>
  <h1>Orthodox Easter Calculator</h1>
  <p>Enter a year and see the year day for Orthodox Easter using Gauss formula.</p>
  <label for="year">Year:</label>
  <input type="number" id="year" min="0" max="9999">
  <button id="button">Calculate</button>
  <p id="result">0</p>

  <script>
    // return difference in days between Julian and Gregorian calendars
const months = [
    "January",   "February", "March",    "April",
    "May",       "June",     "July",     "August",
    "September", "October",  "November", "December",
];

function j2g(year) {
    return year < 1500 ? 0 : 10 + Math.floor(year / 100 - 16) - Math.floor((year / 100 - 16) / 4);
}

function isLeapYear(y) {
    return ((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0);
}

function paskha(year) {
    let dt = {
      month:"",
      day:0,
    };
    let a = year % 19;
    let b = year % 4;
    let c = year % 7;
    let d = (19 * a + 15) % 30;
    let e = (2 * b + 4 * c + 6 * d + 6) % 7;
    let cumday = isLeapYear(year) ? [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335] : [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
    let i = 0;
    dayOfYear = cumday[2] + 22 + d + e + j2g(year);
    while (cumday[i] < dayOfYear) {
        i+=1;
    }
    dt.month = months[i-1];
    dt.day =  dayOfYear - cumday[i-1];
    return dt;
}

    // get the input element by id
    var input = document.getElementById("year");

    // get the button element by id
    var button = document.getElementById("button");

    // add an event listener to handle button click
    button.addEventListener("click", function() {

      // get the input value as a number
      var year = Number(input.value);

      // check if the input is a valid year
      if (isNaN(year) || year < 0 || year > 9999) {
        // display an error message
        document.getElementById("result").innerHTML = "Please enter a valid year between 0 and 9999.";
        return;
      }

      // calculate the year day for Orthodox Easter
      var dt = paskha(year);

      // display the result
      document.getElementById("result").innerHTML = "The year day for Orthodox Easter in " + year + " is " +
        dt.month + " " + dt.day + ".";
    });
  </script>
</body>
</html>
	<!DOCTYPE html>
	<html>
	<head>
	<title>Orthodox Easter Calculator</title>
	</head>
	<body>
	<h1>Orthodox Easter Calculator</h1>
	<p>Enter a year and see the year day for Orthodox Easter using Gauss formula.</p>
	<label for="year">Year:</label>
	<input type="number" id="year" min="0" max="9999">
	<button id="button">Calculate</button>
	<p id="result">0</p>

	<script>
	// return difference in days between Julian and Gregorian calendars
	const months = [
	"January", "February", "March", "April",
	"May", "June", "July", "August",
	"September", "October", "November", "December",
	];

	function j2g(year) {
	return year < 1500 ? 0 : 10 + Math.floor(year / 100 - 16) - Math.floor((year / 100 - 16) / 4);
	}

	function isLeapYear(y) {
	return ((y % 4 == 0) && (y % 100 != 0)) \|\| (y % 400 == 0);
	}

	function paskha(year) {
	let dt = {
	month:"",
	day:0,
	};
	let a = year % 19;
	let b = year % 4;
	let c = year % 7;
	let d = (19 * a + 15) % 30;
	let e = (2 * b + 4 * c + 6 * d + 6) % 7;
	let cumday = isLeapYear(year) ? [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335] : [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
	let i = 0;
	dayOfYear = cumday[2] + 22 + d + e + j2g(year);
	while (cumday[i] < dayOfYear) {
	i+=1;
	}
	dt.month = months[i-1];
	dt.day = dayOfYear - cumday[i-1];
	return dt;
	}

	// get the input element by id
	var input = document.getElementById("year");

	// get the button element by id
	var button = document.getElementById("button");

	// add an event listener to handle button click
	button.addEventListener("click", function() {

	// get the input value as a number
	var year = Number(input.value);

	// check if the input is a valid year
	if (isNaN(year) \|\| year < 0 \|\| year > 9999) {
	// display an error message
	document.getElementById("result").innerHTML = "Please enter a valid year between 0 and 9999.";
	return;
	}

	// calculate the year day for Orthodox Easter
	var dt = paskha(year);

	// display the result
	document.getElementById("result").innerHTML = "The year day for Orthodox Easter in " + year + " is " +
	dt.month + " " + dt.day + ".";
	});
	</script>
	</body>
	</html>