How to count days excluding weekends/holidays or only weekends/holidays in JS

Sample

Please enter a date

is from today

days later, and

there are weekdays,

and weekends/holidays.

You can create a program like this.

Date Calculation and Holiday Library

First, as preliminary knowledge, let's look at how to calculate dates and how to determine weekends/holidays.

If you simply want to find the difference between two dates,

you can count them this way,

let date1 = new Date('2023-10-01');
let date2 = new Date('2023-10-11');
return Math.ceil((date2 - date1) / 86400000); // 10

However, this time, to determine if it's a weekend or holiday, we need to examine each date individually.

So, we count them roughly this way.

let date1 = new Date('2023-10-01');
let date2 = new Date('2023-10-11');
let count = 0;
//date1 is incremented by 1 as long as date2 is greater
while(date2 >= date1){
	//add 1 day to date1
	date1.setDate(date1.getDate() + 1);
	//get day of the week 0=Sunday 6=Saturday
	let week = date1.getDay();
	//check if it's a holiday (holiday name if it is, undefined if not)
	let is_holiday = JapaneseHolidays.isHoliday(date1);
	//if it's neither a weekend nor a holiday
	if(week != 0 && week != 6 && !is_holiday){
		++count;
	}
}
return count; // 5

<script src="https://cdn.rawgit.com/osamutake/japanese-holidays-js/v1.0.10/lib/japanese-holidays.min.js"></script>
<script>
let date = new Date();
let is_holiday = JapaneseHolidays.isHoliday(date);
</script>

Count only weekdays

You can count only weekdays with code like the following.

//Count weekdays
function weekdays(input){
	//Get today
	let today = new Date();
	//Count
	let count = 0;
	//today is incremented by 1 as long as input is greater than today
	while(input >= today){
		//add 1 day to today
		today.setDate(today.getDate() + 1);
		//get day of the week 0=Sunday 6=Saturday
		let week = today.getDay();
		//check if it's a holiday (holiday name if it is, undefined if not)
		let is_holiday = JapaneseHolidays.isHoliday(today);
		//if it's neither a weekend nor a holiday
		if(week != 0 && week != 6 && !is_holiday){
			++count;
		}
	}
	return count;
}

weekdays(new Date('2023-10-11')); // 8 (if today is 2023-10-01)

The `while` loop iterates through each date, and `count` is incremented only for weekdays.

However, if 'input' is smaller than 'today', meaning it's a past date,
it won't enter the `while` loop and cannot be counted. Please refer to the section How to handle past dates.

Also, as mentioned earlier, don't forget to load 'japanese-holidays-js'.

PR

//if it's a weekend or a holiday
if(week == 0 || week == 6 || is_holiday){

//Count weekdays or weekends/holidays
function days(input, weekday){
	//Get today
	let today = new Date();
	//Count
	let count = 0;
	//today is incremented by 1 as long as input is greater than today
	while(input >= today){
		//add 1 day to today
		today.setDate(today.getDate() + 1);
		//get day of the week 0=Sunday 6=Saturday
		let week = today.getDay();
		//check if it's a holiday (holiday name if it is, undefined if not)
		let is_holiday = JapaneseHolidays.isHoliday(today);
		//if weekday is true, count weekdays
		if(weekday){
			//if it's neither a weekend nor a holiday
			if(week != 0 && week != 6 && !is_holiday){
				++count;
			}
		}else{
			//if it's a weekend or a holiday
			if(week == 0 || week == 6 || is_holiday){
				++count;
			}
		}
	}
	return count;
}

days(new Date('2023-10-11'), true); // To count only weekdays
days(new Date('2023-10-11'), false); // To count only weekends/holidays

How to handle past dates

Above, we counted 'How many weekdays are there until (a future date)?' To handle past dates as well, you'll likely need to add a conditional branch and another `while` loop.

So, here's the code that also handles past dates.

//Count weekdays
function weekdays(input){
	let today = new Date();
	let count = 0;
	//if the input date is in the future
	if(input - today > 0){
		while(input >= today){
			//add 1 to today
			today.setDate(today.getDate() + 1);
			//get day of the week 0=Sunday 6=Saturday
			let week = today.getDay();
			//check if it's a holiday (holiday name if it is, undefined if not)
			let is_holiday = JapaneseHolidays.isHoliday(today);
			//if it's neither a weekend nor a holiday
			if(week != 0 && week != 6 && !is_holiday){
				++count;
			}
		}
	}else{
		while(input <= today){
			//subtract 1 from today
			today.setDate(today.getDate() - 1);
			//get day of the week 0=Sunday 6=Saturday
			let week = today.getDay();
			//check if it's a holiday (holiday name if it is, undefined if not)
			let is_holiday = JapaneseHolidays.isHoliday(today);
			//if it's neither a weekend nor a holiday
			if(week != 0 && week != 6 && !is_holiday){
				--count;
			}
		}
		//add 1 if it's negative
		++count;
	}
	return count;
}

weekdays(new Date('2023-10-01')); // -8 (if today is 2023-10-11)
weekdays(new Date('2023-10-21')); // 8 (if today is 2023-10-11)

In this code, if the input is a past date, the weekday count will be something like -1.

Similarly, to count only weekends/holidays, change the `if` statements on lines 15 and 28 as follows.

//if it's a weekend or a holiday
if(week == 0 || week == 6 || is_holiday){

Comments

We also welcome reports such as 'It worked!'

• 2024-06-12

  Anonymous

  Thank you for publishing such an article for free.

  I'm so grateful for the easy-to-understand explanation for web beginners!

  I implemented the sample that allows selecting a date 'X business days later', excluding weekends/holidays and specific dates, by copy-pasting. How can I change the display format to [YYYY年MM月DD日]?

  It would be great if I could also display the day of the week. If possible, I would appreciate it if you could advise me.

• 2024-06-12

  Owner

  To Anonymous #001.

  Perhaps this comment is for this article, not this one...?

  I've added a postscript to here, so please check it.