JavaScript implementation of Easter Algorithms

easterAlgos.js

// Algorithm by Tom O’Beirne
// (1961) Puzzles and Paradoxes. New Scientist, No. 228, p. 829, Table 1
// https://books.google.com/books?id=zfzhCoOHurwC&pg=PA829
//
// Implementation in JavaScript by Aldo Fregoso.
// Released under public domain without any kind of warranty or support.
//
function oBeirnesEasterAlgo(x) {
	assert(x != 0, "Year zero does not exist in the Anno Domini (AD) calendar year system.");
	if (x <= 1582) {
		console.warn("Gregorian Calendar took effect on October, 1582.");
	}
	const a = x % 19;
	const b = ~~(x / 100);
	const c = x % 100;
	const d = ~~(b / 4);
	const e = b % 4;
	const g = ~~((8 * b + 13) / 25);
	const h = (19 * a + b - d - g + 15) % 30;
	const i = ~~(c / 4);
	const k = c % 4;
	const l = (2 * e + 2 * i - h - k + 32) % 7;
	const m = ~~((a + 11 * h + 19 * l) / 433);
	const n = ~~((h + l - 7 * m + 90) / 25);
	const p = (h + l - 7 * m + 33 * n + 19) % 32;
	const year = x.toString(10).padStart(4, '0');
	const month = n.toString(10).padStart(2, '0');
	const day = p.toString(10).padStart(2, '0');
	return `${year}-${month}-${day}`;
}

// Algorithm by Jean Meeus
// (1991) Astronomical Algorithms, p. 69
// https://books.google.com/books?id=PU7XxnmcDwYC&pg=PA69
//
// Implementation in JavaScript by Aldo Fregoso.
// Released under public domain without any kind of warranty or support.
//
function meeusJulianEasterAlgo(x) {
	assert(x != 0, "Year zero does not exist in the Anno Domini (AD) calendar year system.");
	if (x < -45) {
		console.warn("Julian Calendar took effect on January 1st, 45 BC.");
	}
	if (x < 33) {
		console.info('Resurrection Sunday most likely happened at April 3rd, AD 33.');
	}
	if (x < 200) {
		console.warn('The algorithm returns non-Sundays for years < 200.');
	}
	const a = x % 4;
	const b = x % 7;
	const c = x % 19;
	const d = (19 * c + 15) % 30;
	const e = (2 * a + 4 * b - d + 34) % 7;
	const f = d + e + 114;
	const g = ~~(f / 31);
	const h = (f % 31) + 1;
	const year = x.toString(10).padStart(4, '0');
	const month = g.toString(10).padStart(2, '0');
	const day = h.toString(10).padStart(2, '0');
	return `${year}-${month}-${day}`;
}