caldulated day of week with zellersCongruence, by GPT-4

zellersCongruence.js

// Zeller's Congruence function
function zellersCongruence(year, month, day) {
  if (month < 3) {
    month += 12;
    year -= 1;
  }

  const A = year % 100;
  const B = Math.floor(year / 100);
  const F = A + Math.floor(A / 4) + Math.floor(B / 4) - 2 * B + Math.floor(13 * (month + 1) / 5) + day;
  let result = ((F % 7) + 7) % 7;

  // Adjust the result so that 0 represents Sunday, 1 represents Monday, and so on
  if (result === 0) {
    result = 7;
  }
  return result - 1;
}

// Function to get the day of the week using JavaScript Date object
function getDayOfWeek(year, month, day) {
  const date = new Date(year, month - 1, day);
  return date.getDay();
}

// Simple assert function
function assertEqual(actual, expected, message) {
  if (actual === expected) {
    console.log(`[PASSED] ${message}`);
  } else {
    console.error(`[FAILED] ${message}: expected ${expected}, but got ${actual}`);
  }
}

// Test cases for Zeller's Congruence function
function testZellersCongruence() {
  const testCases = [
    { year: 2023, month: 8, day: 13 },
    { year: 2021, month: 1, day: 1 },
    { year: 2000, month: 12, day: 31 },
    { year: 1987, month: 10, day: 11 },
    { year: 1776, month: 7, day: 4 },
  ];

  testCases.forEach(({ year, month, day }) => {
    const expectedResult = getDayOfWeek(year, month, day);
    const actualResult = zellersCongruence(year, month, day);
    const message = `${year}-${month}-${day} should be ${expectedResult}`;
    assertEqual(actualResult, expectedResult, message);
  });
}

// Run the tests
testZellersCongruence();

// [PASSED] 2023-8-13 should be 0
// [PASSED] 2021-1-1 should be 5
// [PASSED] 2000-12-31 should be 0
// [PASSED] 1987-10-11 should be 0
// [PASSED] 1776-7-4 should be 4