JavaScript: Difference between two dates in days

JavaScript Datetime: Exercise-8 with Solution

Date Difference in Days

Write a JavaScript function to get the difference between two dates in days.

Test Data:
console.log(date_diff_indays('04/02/2014', '11/04/2014'));
console.log(date_diff_indays('12/02/2014', '11/04/2014'));
Output :
216
-28

Sample Solution:

JavaScript Code:

// Define a JavaScript function called date_diff_indays with parameters date1 and date2
var date_diff_indays = function(date1, date2) {
    // Create a new Date object representing the first date
    dt1 = new Date(date1);
    // Create a new Date object representing the second date
    dt2 = new Date(date2);
    // Calculate the difference in days between the two dates
    return Math.floor((Date.UTC(dt2.getFullYear(), dt2.getMonth(), dt2.getDate()) - Date.UTC(dt1.getFullYear(), dt1.getMonth(), dt1.getDate())) / (1000 * 60 * 60 * 24));
}

// Output the difference in days between '04/02/2014' and '11/04/2014'
console.log(date_diff_indays('04/02/2014', '11/04/2014'));
// Output the difference in days between '12/02/2014' and '11/04/2014'
console.log(date_diff_indays('12/02/2014', '11/04/2014'));

Output:

216
-28

Explanation:

In the exercise above,

• The code defines a JavaScript function named "date_diff_indays()" with two parameters: 'date1' and 'date2', representing two date strings.
• Inside the function:
• It creates new Date objects 'dt1' and 'dt2' by parsing the provided date strings 'date1' and 'date2', respectively.
• It calculates the difference in days between the two dates using the following steps:
• It converts both dates to UTC using Date.UTC(), which returns the number of milliseconds since January 1, 1970, 00:00:00 UTC for each date.
• It then subtracts the UTC timestamp of 'dt1' from the UTC timestamp of 'dt2' to get the difference in milliseconds between the two dates.
• Finally, it divides the difference in milliseconds by the number of milliseconds in a day (1000 milliseconds 60 seconds 60 minutes * 24 hours) to obtain the difference in days. The "Math.floor()" function is used to round down the result to the nearest integer.
• The function returns the calculated difference in days.
• The code then demonstrates the "date_diff_indays()" function by calling it with two different date pairs:
• '04/02/2014' and '11/04/2014'
• '12/02/2014' and '11/04/2014'

Flowchart:

Live Demo:

See the Pen JavaScript - Difference between two dates in days-date-ex- 8 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that calculates the difference in days between two dates by subtracting their timestamps and dividing by the number of milliseconds per day.
• Write a JavaScript function that uses Math.floor to return the integer day difference between two Date objects.
• Write a JavaScript function that accepts date strings, converts them to Date objects, and returns the signed day difference.
• Write a JavaScript function that handles daylight saving time changes when computing the day difference.

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