How to calculate the time difference (days, hours, minutes) between two dates in JavaScript

In this tutorial, I will guide you on how to write a function that calculates the time difference between two JavaScript Date objects and return the calculation of the difference in days, hours, and minutes.

You can get the javascript difference between date objects by subtracting the date Objects. It will return the difference in milliseconds.

const diffInMilliseconds = Math.abs(new Date('2019/10/1 00:00:00') - new Date('2019/10/2 00:00:00'));

console.log(diffInMilliseconds); //86400000

In the above example, I have subtracted two date objects which returns the milliseconds. Math.abs is used to get positive numbers. The above example return 86500000 (milliseconds) which is exactly 1 day.

Calculate Time Difference between two dates in JavaScript

function timeDiffCalc(dateFuture, dateNow) {
    let diffInMilliSeconds = Math.abs(dateFuture - dateNow) / 1000;

    // calculate days
    const days = Math.floor(diffInMilliSeconds / 86400);
    diffInMilliSeconds -= days * 86400;
    console.log('calculated days', days);

    // calculate hours
    const hours = Math.floor(diffInMilliSeconds / 3600) % 24;
    diffInMilliSeconds -= hours * 3600;
    console.log('calculated hours', hours);

    // calculate minutes
    const minutes = Math.floor(diffInMilliSeconds / 60) % 60;
    diffInMilliSeconds -= minutes * 60;
    console.log('minutes', minutes);

    let difference = '';
    if (days > 0) {
      difference += (days === 1) ? `${days} day, ` : `${days} days, `;
    }

    difference += (hours === 0 || hours === 1) ? `${hours} hour, ` : `${hours} hours, `;

    difference += (minutes === 0 || hours === 1) ? `${minutes} minutes` : `${minutes} minutes`; 

    return difference;
  }

  console.log(timeDiffCalc(new Date('2019/10/1 04:10:00'), new Date('2019/10/2 18:20:00')));

// the time difference is:
// 1 day, 14 hours, 10 minutes

The above function will work perfectly to calculate the time difference (except daylight saving) between two dates.

The first line of the function is to get the time difference in milliseconds by subtracting two Date objects. From that milliseconds, we can calculate days, hours, and minutes. I will explain it step by step below.

Calculate The Number of Days Between Two Dates in JavaScript

// calculate (and subtract) whole days
const days = Math.floor(diffInMilliSeconds / 86400);
diffInMilliSeconds -= days * 86400;
console.log('calculated days', days);

To calculate the number of days difference between two objects, we should divide the diffInMilliSeconds (time difference in milliseconds) with 86400 (which is the number of seconds per day).

After that, we should subtract the days in diffInMilliSeconds with the number of days in milliseconds (days * 86400) for further accurate calculation of hours and minutes.

Calculate Hours Difference between Two Dates in JavaScript

// calculate hours
const hours = Math.floor(diffInMilliSeconds / 3600) % 24;
diffInMilliSeconds -= hours * 3600;
console.log('calculated hours', hours);

To calculate the hours difference of the two dates, we should divide the diffInMilliSeconds with 3600 which is the milliseconds of 1 hour, and then further divide it by 24 (24 hours per day) and get the remainder using modules operator. After that, subtract the diffInMilliSeconds with the number of hours in milliseconds (hours * 3600) for further calculation of minutes.

Calculate Minutes Difference between Two Date in JavaScript

// calculate minutes
const minutes = Math.floor(diffInMilliSeconds / 60) % 60;
diffInMilliSeconds -= minutes * 60;
console.log('minutes', minutes);

To calculate the minutes difference between two dates, we should divide the diffInMilliSecondswith 60 seconds) and then get the remainder by dividing it by 60 (60 minutes per hour). After that, subtract the diffInMilliSeconds with the number of minutes in milliseconds (minutes * 60).

Conclusion

I hope, you have learned to play with the Date to calculate the time difference in JavaScript. The above method will work for most of the situations. If you have to manage the daylight saving in your calculation this method is not recommended. I highly recommend you to use countdown.js for overcoming the daylight saving issue. Thank you.