Find the difference between Dates in JavaScript

Learn how to find difference between two dates in JavaScript.

We learn about finding Number of Seconds , Number of Minutes , Number of hours , Number of days , Number of weeks , Number of months , Number of years between two dates.

Let’s create two dates

let d1 = Date.now();

let d2 = new Date(2019,5,22).getTime(); //Jun 22 2019 in millisecond

console.log(d1); //1573527098946

console.log(d2); //1561141800000

Number of Seconds between two dates.

1 second = 1000 milliseconds 

Now we are having two date d1 and d2 in milliseconds. To convert milliseconds into seconds ,we can divide the difference between two dates in milliseconds by 1000 .

function secondsDiff(d1, d2) {

   let millisecondDiff = d2 - d1;

   let secDiff = Math.floor( ( d2 - d1) / 1000 );

   return secDiff;

}

Number of Minutes between two dates.

1 minutes = 60 seconds

Now we have method to find the number of seconds between two dates , so we can find seconds difference, then divide that by 60 will give us the number of minutes between two dates.

function minutesDiff(d1, d2) {

     let seconds = secondsDiff(d1, d2);

     let minutesDiff = Math.floor( seconds / 60 );

     return minutesDiff;

}

Number of Hours between two dates.

1 hour = 60 minutes

Now we have method to find the number of minutes between two dates , so we can find minutes difference, then divide that by 60 will give us the number of hours between two dates .

function hoursDiff(d1, d2) {

   let minutes = minutesDiff(d1, d2);

   let hoursDiff = Math.floor( minutes / 60 );

   return hoursDiff;

}

Number of Days between two dates.

1 day = 24 hours 

Now we have method to find the number of hours between two dates , so we can find difference, then divide that by 24 will give us the number of days between two dates.

function daysDiff(d1, d2) {

   let hours = hoursDiff(d1, d2);

   let daysDiff = Math.floor( hours / 24 );

   return daysDiff;

}

Number of Weeks between two dates.

1 week = 7 days

Now we have method to find the number of days between two dates , so we can find difference, then divide that by 7 will give us the number of weeks between two dates.

function weeksDiff(d1, d2) {

   let days = daysDiff(d1, d2);

   let weeksDiff = Math.floor( days/ 7 );

   return weeksDiff;

}

Number of Years between two dates.

To find number of years between two dates we have in-built method getFullYear , Subtract the date2 year with date1 year, we will get yearsDiff .

function yearsDiff(d1, d2) {

    let date1 = new Date(d1);

    let date2 = new Date(d2);

    let yearsDiff =  date2.getFullYear() - date1.getFullYear();

    return yearsDiff;

}

Number of Months between two dates.

1 month != 30 days 

Number of days in month is not same in all months , so we need to do it differently

Steps :

• First we need to find number of years between two dates.
• Multiply number of years between two dates by 12(because for each year 12 months)
• Subtract the month number(June → 5) of second date with the month number of first date

Finding number of months between two dates

function monthsDiff(d1, d2) {

  let date1 = new Date(d1);

  let date2 = new Date(d2);

  let years = yearsDiff(d1, d2);

  let months =(years * 12) + (date2.getMonth() - date1.getMonth()) ;

  return months;

}

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