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Time Checkers

isLeapYear​

Checks if a given year is a leap year according to the Gregorian calendar rules.

Function Signature​

function isLeapYear(year: Numeric): boolean;

Parameters​

  • year: The year to check (can be number or numeric string)

Returns​

true if the year is a leap year, false otherwise

Leap Year Rules​

A year is a leap year if:

  1. It's divisible by 4 AND not divisible by 100
    OR
  2. It's divisible by 400

Example Usage​

import { isLeapYear } from 'nhb-toolbox';

console.log(isLeapYear(2000));  // true (divisible by 400)
console.log(isLeapYear(2020));  // true (divisible by 4 but not 100)
console.log(isLeapYear(1900));  // false (divisible by 100 but not 400)
console.log(isLeapYear("2024")); // true (accepts numeric strings)

Notes​

  • Handles both numbers and numeric strings
  • Follows Gregorian calendar rules
  • Works with negative years (BC dates)
  • Returns false for non-numeric inputs

Type Definition​

type Numeric = number | `${number}`;

Use Cases​

  • Date validation
  • Calendar applications
  • Age calculations
  • Date arithmetic
  • Financial year calculations

Conclusion​

The isLeapYear function provides:

  1. Accurate leap year detection
  2. Flexible input (numbers or strings)
  3. Historical accuracy for BC dates
  4. Simple integration with date logic

Ideal for applications requiring:

  • Calendar displays
  • Date pickers
  • Age verification
  • Time-sensitive calculations