When working with dates in JavaScript , calculating the difference between two dates is easy if you only need calendar days.

But in real business use cases, we often need to calculate business days , also called working days .

Business days usually exclude Saturdays and Sundays. In some cases, public holidays also need to be excluded.

I created a free online Business Days Calculator for checking this quickly:

https://greatuptools.com/business-days-calculator

What are business days?

Business days usually mean Monday to Friday.

Saturday and Sunday are normally excluded because they are weekends.

For example:

Business days: Monday, Tuesday, Wednesday, Thursday, Friday

Weekend days: Saturday, Sunday

Basic JavaScript date difference

If you only want the number of calendar days between two dates, you can subtract two dates in JavaScript :

Code example:

const startDate = new Date("2026-01-01");

const endDate = new Date("2026-12-31");

const millisecondsPerDay = 1000 * 60 * 60 * 24;

const…