Add function to add date and time to date object in PHP

Add calendar intervals to a date

DateTime::add() changes a mutable DateTime object, while DateTimeImmutable::add() returns a new object. DateInterval expresses the amount to add.

$start = new DateTimeImmutable('2026-09-14');
$next = $start->add(new DateInterval('P10D'));
echo $start->format('Y-m-d') . "
";
echo $next->format('Y-m-d');

Month and year additions follow calendar rules, so check end-of-month behavior when it matters to your application.

WE will learn how to add date time intervals to a date object. We must understand date interval and date format before using add function to the date object.

Use DateTimeImmutable when additions should return a new object without changing the original date. Use DateTime when in-place mutation is intentional.

Procedural style

$date = date_create('2019-01-05');
date_add($date, date_interval_create_from_date_string('15 days'));
echo date_format($date, 'Y-m-d'); // Output is 2019-01-20

Object oriented style.

$date1=new DateTime('2019-05-30'); // date object created. 
$new_date=$date1->add(new DateInterval('P1Y3M')); // inerval of 1 year 3 months 
echo $new_date->format('Y-M-d'); // Output is 2020-Aug-30

Let us try to add 5 days to current date.

date_default_timezone_set ("Asia/Kolkata");
$date=new DateTime("now") ;
echo $date->format('d-m-y');
echo "<br>";
$date=$date->add(new DateInterval('P5D'));
echo $date->format('d-m-y ');

The output is here

20-10-26
25-10-26

We will add 1 Year, 3 months , 5 days to current date . We will only change the affected row in above code like this.

$date=$date->add(new DateInterval('P1Y3M5D'));

echo $date->format('m-d-y ');

Let us add hour minute and seconds to this date object.


date_default_timezone_set ("Asia/Kolkata");
$date=new DateTime("now") ;
echo $date->format('d-m-y H:i:s');
echo "<br>";
$date=$date->add(new DateInterval('P1Y3M5DT4H5M12S'));
echo $date->format('m-d-y H:i:s ');

Output is here ( Refresh this page to see the change in output)

20-10-26 10:37:35
01-25-28 14:42:47

Using DateTimeImmutable object

DateTimeImmutable never modifies itself but returns a new object instead

$date1=new DateTime('2019-05-30'); // date object created. 
$date1->add(new DateInterval('P1Y3M')); // inerval of 1 year 3 months added
echo $date1->format('Y-M-d'); // Output is 2020-Aug-30
/// by using DateTimeImmutable ///
$date1=new DateTimeImmutable('2019-05-30'); // original object
$date2=$date1->add(new DateInterval('P1Y3M')); // returned object has new date
echo $date1->format('Y-M-d'); // 2019-May-30
echo $date2->format('Y-M-d'); // 2020-Aug-30

In case of date object created using DateTimeImmutable after adding the interval the original value never changes.
PHP Date Functions diff(): Difference in two dates

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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date_add() : adds a specified interval to a DateTime object

Add calendar intervals to a date

Using DateTimeImmutable object

Subhendu Mohapatra