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// Zeller's Congruence Algorithm finds the day of the week from the Gregorian Date. Wikipedia: https://en.wikipedia.org/wiki/Zeller%27s_congruence

export const zellersCongruenceAlgorithm = (day, month, year) => {

if (typeof day !== 'number' || typeof month !== 'number' || typeof year !== 'number') {

throw new TypeError('Arguments are not all numbers.')

}

const q = day

let m = month

let y = year

if (month < 3) {

m += 12

y -= 1

}

day =

(q + Math.floor(26 * (m + 1) / 10) + (y % 100) + Math.floor((y % 100) / 4) + Math.floor(Math.floor(y / 100) / 4) + (5 * Math.floor(y / 100))) %

const days = [

'Saturday',

'Sunday',

'Monday',

'Tuesday',

'Wednesday',

'Thursday',

'Friday'

]

return days[day]

}