TheAlgorithms/JavaScript · error · TypeError

Arguments are not all numbers.

Error message

Arguments are not all numbers.

What it means

Thrown by `zellersCongruenceAlgorithm(day, month, year)` when any of the three arguments fails `typeof === 'number'`. The Gregorian-date formula uses arithmetic on all three, so non-numbers break it. The check is type-only - NaN passes and yields garbage.

Source

Thrown at Maths/ZellersCongruenceAlgorithm.js:8

// 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)) %
    7
  const days = [
    'Saturday',

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Coerce all three arguments with `Number(...)` and verify each is a finite integer.
2. When reading from a Date object, use `.getDate()`, `.getMonth() + 1`, `.getFullYear()` (all numbers).
3. Validate range (1-31 day, 1-12 month, positive year) in addition to type.

Example fix

// before
zellersCongruenceAlgorithm(req.query.day, req.query.month, req.query.year)

// after
const [d, m, y] = [req.query.day, req.query.month, req.query.year].map(Number)
if (![d, m, y].every((v) => Number.isInteger(v))) throw new TypeError('all date parts must be integers')
zellersCongruenceAlgorithm(d, m, y)

const [d, m, y] = [day, month, year].map(Number)
if (![d, m, y].every((v) => typeof v === 'number' && Number.isInteger(v))) {
  throw new TypeError('day, month, year must all be integers')
}
zellersCongruenceAlgorithm(d, m, y)

const isInt = (x) => typeof x === 'number' && Number.isInteger(x)

When it happens

Trigger: Call `zellersCongruenceAlgorithm('1', 1, 2020)`, `zellersCongruenceAlgorithm(1, 'Jan', 2020)`, `zellersCongruenceAlgorithm(1, 1, null)`, or any case where a Date component is stringified.

Common situations: Date components read from URL params, CSV cells, or `Date` parts passed as strings; mixing the function with `moment.format('M')` (string) outputs.

Related errors

• Argument not an Integer
• Provided input is not an array
• Invalid capacity
• Rule must be an integer between the values 0 and 255 (got ${
• Coefficient a, b should be number

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/e464fa7e82a6b650. Report an issue: GitHub.