chrono-holidays

An extension for chrono to provide parsing for holidays.

It knows things like thanksgiving in 2017 and christmas!

Usage

$ yarn add chrono-holidays

(or use npm, I'm not picky).

Then, from code (all examples here are es2015, but it works just as well in es5):

import chrono from 'chrono-holidays';

const xmas = chrono.parseDate('christmas');
// xmas is a Date object for December 25 of the current year

So you want even more holidays?

The object you get from importing chrono-holidays has an addHoliday method that accepts a holiday in the format in the json files. For example,

import chrono from 'chrono-holidays';
chrono.addHoliday({
    name: "robert'?s birthday",
    type: 'abs',
    month: 11,
    date: 5,
});

chrono.parseDate("robert's birthday", new Date(2018,1,1)).toDateString()
// returns 'Mon Nov 05 2018'

Why not merge into chrono?

I don't want people to have to install holidays if they don't care. I expect the JSON files will end up getting fairly large. This doesn't duplicate chrono though, just includes it and uses its excellent custom parser support.

Contributing

Commit yarn.lock, not package-lock.json. Add holidays. Fix bugs. As long as it passes tests, you're good to go and I'll almost certainly accept your MR.

Add at least one test for every new holiday by putting a json file in test/holidays/ that matches the format of the ones already there (or edit an existing file).

Holidays json files

There are two types of holidays.

Relative ("type": "rel") holidays are like Thanksgiving, the fourth Thursday of November. That is, it is identified by a month, day of week, and week count. Day of week is indexed with 0 for Sunday, the same way JavaSCript's Date uses the day field. Months start with January at 1, and the first week of the month is "nth": 1. The last week of the month is "nth": -1.

Absolute holidays are like Christmas, December 25. They are identified by a month and date.

The name field is actually a regex. Slashes must be escaped twice, since it must be expressed as a string to be stored in JSON. However, it will be made case-insensitive, and all literal spaces will be replaced with /\s+/ to allow for any whitespace, so you shouldn't need many slashes if any. Do be aware that this means that a character class with a space won't work, because /[ +-]/ will expand to /[(?:\s+)+-]/ which is not at all what you want. In that case, use a capture group with an or: /( |[+-])/.

Test json files

The test json files are just an object with input strings (date-qualified) as the keys and expected dates parsable by new Date() as the values. Every entry will be tested against the custom parser.