Calculate the number of days between 2 dates in JavaScript

Published July 20, 2020

Calculate the number of days between 2 dates

Consider this 2 dates,

// 2 dates
const date1 = new Date("September 03, 1998");
const date2 = new Date(); // will return current date

You can also provide the date in MM/DD/YYYY format also into the Date() constructor function.

To find the number of the days between any 2 dates, we need to rely on some calculations as javascript itself doesn't provide any methods to do that.

First, we need to get the milliseconds between these 2 dates.

// 2 dates
const date1 = new Date("September 03, 1998");
const date2 = new Date(); // will return current date

// get milliseconds
const millisecondsBetween2Dates = Math.abs(date2 - date1);

We are using the Math.abs() to get the absolute value so that it deals with negative values also.

Secondly, we need to get the number of days using these milliseconds.

// 2 dates
const date1 = new Date("September 03, 1998");
const date2 = new Date(); // will return current date

// get milliseconds
const millisecondsBetween2Dates = Math.abs(date2 - date1);

// get number of days
const numberOfDays = Math.ceil(
  millisecondsBetween2Dates / (1000 * 60 * 60 * 24)
);

console.log(numberOfDays);

We are using the Math.ceil() to round to the next largest integer.

To convert it into the days we are dividing it with 1000 (milliseconds)* 60 (seconds) * 60 (minutes) * 24 (hours).

NOTE: 1 second is 1000 milliseconds.

We are dividing the total milliseconds with 1000

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