Calculate Second Monday of the month in javascript (not quite done)

gistfile1.js

/*jslint plusplus:true, white:true */
/*global console:false */

function secondMonday(year, month) { "use strict";
        var firstDay = new Date(year, month, 1);
        if(firstDay.getDay() !== 1) {
                firstDay.setDate(
                        firstDay.getDay() === 0 ? 2 :  9 - firstDay.getDay()
                );
        }
        firstDay.setDate(firstDay.getDate() + 7);
        return firstDay;
}


var year, month;
for(year=2017;year>2013;--year) {
        for(month=0;month<12;++month) {
                console.log(secondMonday(year, 11-month) + "\n");
        }
}

Hey, I created a script to get the date of any ordinal weekday (e.g. “first Sunday”, or “third Tuesday”). Posting here for anyone else interested.

// Script to get date of ordinal weekday.
let year = 2022, month = 7, ordinal = 1, weekday = 'Sun' // Get date for first Sunday of August 2022

let d = new Date(year, month, 1)

d.setUTCHours(0, 0, 0, 0)

const dayOfWeek = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'].findIndex(x => x === weekday)

const ORDINALCONST =
  7 * ordinal + dayOfWeek - d.getUTCDay() - (d.getUTCDay() <= dayOfWeek ? 7 : 0)

d.setUTCDate(d.getUTCDate() + ORDINALCONST)

console.log(ordinal, weekday, d)

@heymartinadams looks amazing.

But it seems there is a bug, for example with the following parameters:
let year = 2022, month = 8, ordinal = 1, weekday = 'Wed'

thre result is 2022-08-31T00:00:00.000Z

but it should be 2022-09-07T00:00:00.000Z, not?

i think it should be

7 * ordinal + dayOfWeek - date.getUTCDay() - (date.getUTCDay() < dayOfWeek ? 7 : 0);

so only < not <= in the last part of the formula (date.getUTCDay() < dayOfWeek ? 7 : 0)

Hey @KevDev99 haven’t verified it (and don’t have the brainpower to do so at the moment — too busy with other stuff), but I’ll take your word for it! Thank you ✨

Had to do another calculation for last [weekday] of the month (e.g. last Sunday of August 2022) — as opposed to first, second, etc. Hat tip to @brucemcpherson for this snippet and to Dennis R. for this snippet:

let year = 2022, month = 7, ordinal = 'last', weekday = 'Sun'

let d

const dayOfWeek = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'].findIndex(x => x === weekday)

// Get the date of the last weekday: e.g. ordinal = 'last', weekday = 'Tue' of the month
if (ordinal === 'last') {
  // Last day of desired month
  d = new Date(year + (month.getMonth() === 11 ? 1 : 0), (month.getMonth() + 1) % 12, 0)

  d.setUTCHours(0, 0, 0, 0)

  // Find out what day of week that is and adjust
  d.setUTCDate(d.getUTCDate() - ((d.getUTCDay() + 7 - dayOfWeek) % 7)) // Note difference btw `getDate()` and `getDay()`

  console.log(ordinal, weekday, d)
}