isLeap

import { isLeap } from "jsr:@ende/datetime";

function

function isLeap(year: Date | number): boolean

Returns whether the given year is a leap year. Passing in a Date object will return the leap year status of the year of that object and take the current timezone into account. Passing in a number will return the leap year status of that number.

This is based on https://docs.microsoft.com/en-us/office/troubleshoot/excel/determine-a-leap-year.

year: Date | number: The year in number or Date format.

Returns

true if the given year is a leap year; false otherwise.

Example: Basic usage

import { isLeap } from "@ende/datetime/is-leap";
import { assertEquals } from "@ende/assert";

assertEquals(isLeap(new Date("1970-01-02")), false);

assertEquals(isLeap(1970), false);

assertEquals(isLeap(new Date("1972-01-02")), true);

assertEquals(isLeap(1972), true);

Example: Accounting for timezones

import { isLeap } from "@ende/datetime/is-leap";

 // True if the local timezone is GMT+0; false if the local timezone is GMT-1
isLeap(new Date("2000-01-01"));

// True regardless of the local timezone
isLeap(2000);

Source