@stdlib/time-day-of-year NPM

dayOfYear

Determine the day of the year.

Installation

npm install @stdlib/time-day-of-year

Usage

var dayOfYear = require( '@stdlib/time-day-of-year' );

dayOfYear( [month[, day, year]] )

Returns the day of the year.

var num = dayOfYear();
// returns <number>

By default, the function returns the day of the year for the current date (according to local time). To determine the day of the year for a particular day, provide month, day, and year arguments.

var num = dayOfYear( 12, 31, 2016 );
// returns 366

num = dayOfYear( 12, 31, 2017 );
// returns 365

A month may be either a month's integer value, three letter abbreviation, or full name (case insensitive).

var num = dayOfYear( 12, 31, 2016 );
// returns 366

num = dayOfYear( 'dec', 31, 2016 );
// returns 366

num = dayOfYear( 'december', 31, 2016 );
// returns 366

The function also supports providing a Date object.

var num = dayOfYear( new Date() );
// returns <number>

Examples

var dayOfYear = require( '@stdlib/time-day-of-year' );

var v;
var i;

for ( i = 0; i < 2021; i++ ) {
    v = dayOfYear( 'Dec', 31, i );
    console.log( 'In the year %d, December 31 is day number %d.', i, v );
}

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.