US Federal Holidays

Builds and returns a list of all US federal holidays for a given year, and
provides a helper method to determine if a given date is a US federal holiday.
Handles shifting holidays to the nearest weekday if the holiday falls on a
weekend.

US federal holidays are as defined by OPM.

$3

``
npm install @18f/us-federal-holidays
`

Requires Node.js 12 or higher.

$3

To get a list of all US federal holidays in a given year, use the allForYear
method. If no year is passed in, uses the current year.

`javascript
const fedHolidays = require('@18f/us-federal-holidays');

const options = { shiftSaturdayHolidays: true, shiftSundayHolidays: true };
const holidays = fedHolidays.allForYear(2016, options);

// Returns
[ { name: 'New Year\'s Day',
date: 2016-01-01T00:00:00.000Z,
dateString: '2016-1-1' },
{ name: 'Birthday of Martin Luther King, Jr.',
date: 2016-01-18T00:00:00.000Z,
dateString: '2016-1-18' },
{ name: 'Washington\'s Birthday',
alsoObservedAs: 'Presidents\' Day',
date: 2016-02-15T00:00:00.000Z,
dateString: '2016-2-15' },
{ name: 'Memorial Day',
date: 2016-05-30T00:00:00.000Z,
dateString: '2016-5-30' },
{
name: 'Juneteenth National Independence Day',
date: 2016-06-20T00:00:00.000Z,
dateString: '2016-6-20' },
{ name: 'Independence Day',
date: 2016-07-04T00:00:00.000Z,
dateString: '2016-7-4' },
{ name: 'Labor Day',
date: 2016-09-05T00:00:00.000Z,
dateString: '2016-9-5' },
{ name: 'Columbus Day',
alsoObservedAs: 'Indigenous Peoples\' Day',
date: 2016-10-10T00:00:00.000Z,
dateString: '2016-10-10' },
{ name: 'Veterans Day',
date: 2016-11-11T00:00:00.000Z,
dateString: '2016-11-11' },
{ name: 'Thanksgiving Day',
date: 2016-11-24T00:00:00.000Z,
dateString: '2016-11-24' },
{ name: 'Christmas Day',
date: 2016-12-26T00:00:00.000Z,
dateString: '2016-12-26' } ]
`

To get a list of all US federal holidays within a date range, use the inRange
method. If no start date is provided in, uses the current date. If the end
date is omitted, one year from the current date is used.

`javascript
const fedHolidays = require('@18f/us-federal-holidays');
const start = new Date('2016-02-13');
const end = new Date('2017-07-23');
const options = { shiftSaturdayHolidays: true, shiftSundayHolidays: true };
const holidays = fedHolidays.federalHolidaysInRange(start, end, options);

// Returns
[ { name: 'Washington\'s Birthday',
date: 2016-02-15T00:00:00.000Z,
dateString: '2016-2-15' },
{ name: 'Memorial Day',
date: 2016-05-30T00:00:00.000Z,
dateString: '2016-5-30' },
{
name: 'Juneteenth National Independence Day'
date: 2016-06-20T00:00:00.000Z,
dateString: '2016-6-20' },
{ name: 'Independence Day',
date: 2016-07-04T00:00:00.000Z,
dateString: '2016-7-4' },
{ name: 'Labor Day',
date: 2016-09-05T00:00:00.000Z,
dateString: '2016-9-5' },
{ name: 'Columbus Day',
alsoObservedAs: 'Indigenous Peoples\' Day',
date: 2016-10-10T00:00:00.000Z,
dateString: '2016-10-10' },
{ name: 'Veterans Day',
date: 2016-11-11T00:00:00.000Z,
dateString: '2016-11-11' },
{ name: 'Thanksgiving Day',
date: 2016-11-24T00:00:00.000Z,
dateString: '2016-11-24' },
{ name: 'Christmas Day',
date: 2016-12-26T00:00:00.000Z,
dateString: '2016-12-26' },
{ name: 'New Year\'s Day',
date: 2017-01-02T00:00:00.000Z,
dateString: '2017-1-2' },
{ name: 'Birthday of Martin Luther King, Jr.',
date: 2017-01-16T00:00:00.000Z,
dateString: '2017-1-16' },
{ name: 'Washington\'s Birthday',
alsoObservedAs: 'Presidents\' Day',
date: 2017-02-20T00:00:00.000Z,
dateString: '2017-2-20' },
{ name: 'Memorial Day',
date: 2017-05-29T00:00:00.000Z,
dateString: '2017-5-29' },
{
name: 'Juneteenth National Independence Day'
date: 2017-06-19T00:00:00.000Z,
dateString: '2017-6-19' },
{ name: 'Independence Day',
date: 2017-07-04T00:00:00.000Z,
dateString: '2017-7-4' } ]
`

To determine if a date is a federal holiday, use the isAHoliday method. If no
argument is provided, defaults to the current date:

`javascript
const fedHolidays = require("@18f/us-federal-holidays");

const options = {
shiftSaturdayHolidays: true,
shiftSundayHolidays: true,
utc: false
};
const isAHoliday = fedHolidays.isAHoliday(myDate, options);
// Returns true or false
`

All three methods take options as a second argument. This argument is a plain
object which accepts the following properties:

`javascript
{
// Whether or not holidays that fall on Saturdays should be
// shifted to Friday observance. If you don't follow the
// US federal standard for observing holidays on weekends,
// you can adjust by setting this value to false.
// Default value is true.
shiftSaturdayHolidays: boolean,

// Whether or not holidays that fall on Sundays should be
// shifted to Monday observance. If you don't follow the
// US federal standard for observing holidays on weekends,
// you can adjust by setting this value to false.
// Default value is true.
shiftSundayHolidays: boolean
}
`

Additionally, isAHoliday takes an options.utc parameter:

`javascript
{
// Whether to treat the first argument as a UTC date instead
// of the local time. Defaults to false. This is useful if
// you're generating dates from UTC timestamps or otherwise
// creating objects from UTC-based dates.
// Default value is false.
// This option only applies to the isAHoliday method.
utc: boolean;
}
``

$3

This project is in the worldwide public domain. As stated in
CONTRIBUTING:

> This project is in the public domain within the United States, and copyright
> and related rights in the work worldwide are waived through the
> CC0 1.0 Universal public domain dedication.
>
> All contributions to this project will be released under the CC0 dedication.
> By submitting a pull request, you are agreeing to comply with this waiver of
> copyright interest.