How to calculate number of days between two dates in Javascript.

In this tutorial, we will learn how to calculate the number of days between two dates using Javascript. Calculating the number of days is common in programming languages, but it is easier in Javascript than in any other language. Calculating the difference in days between two dates is common in real-world scenarios. It is especially used for event planning, project management, or date-based calculations.

Javascript calculates the difference between two dates using a Date object and some basic arithmetic. In JavaScript, the Date object represents a single point in time.

For example, it will be easy to understand,

function calculateDaysBetweenDates(date1, date2) { 
  const startDate = new Date(date1); 
  const endDate = new Date(date2); 
  const differenceInMilliseconds = endDate - startDate; 
  const millisecondsPerDay = 1000 * 60 * 60 * 24; 
  const differenceInDays = differenceInMilliseconds / millisecondsPerDay; 
  return Math.abs(Math.round(differenceInDays)); 
} 
const daysBetween = calculateDaysBetweenDates("2025-01-02", "2025-01-08"); 
console.log(`Number of days: ${daysBetween}`);

Output : Nummber of days: 6

• You can create a Date object using a string, such as “02-01-2025”.
• The new Date() function takes the string and converts it into a date object.
• This will enable you to calculate something like subtracting two dates.

Dates are stored in milliseconds to calculate the difference between end and start dates. To calculate the number of days we need to convert milliseconds into days which makes it easier to calculate. To calculate no. of days we have to divide the difference in milliseconds into milliseconds per day.

Here, Math.abs() is used to get the result positively. Math.round() result is a whole number, accounting for any time discrepancies. This is how we get the number of days.

The number of days between two dates in JavaScript is calculated through a simple yet effective solution for a variety of real-world applications, including event planning, project management, and financial calculations. You can determine date differences using the Date object and basic arithmetic with minimal code. This approach is reliable, versatile, and easy to implement, making it an essential tool for developers in everyday applications.