DateTimeImmutable creates class but it never changes itself when data is modified

Use DateTimeImmutable to avoid accidental mutation

DateTimeImmutable behaves like DateTime for formatting and calculations, but methods such as modify(), add() and setDate() return a new object instead of changing the original.

$original = new DateTimeImmutable('2026-09-14');
$next = $original->modify('+1 week');
echo $original->format('Y-m-d') . "
";
echo $next->format('Y-m-d');

Store the returned object from mutating-style methods; ignoring it leaves the original immutable value unchanged.

We can use DateTimeImmutable in place of DateTime class when we want the original object is not to be modified.

Using date add ...

$date1=new DateTime('2018-04-23'); // date object created. 
$date1->add(new DateInterval('P1Y3M')); // interval of 1 year 3 months added
echo $date1->format('Y-M-d'); // Output is 2019-Jul-23
/// by using DateTimeImmutable ///
$date1=new DateTimeImmutable('2018-04-23'); // date object created . 
$date1->add(new DateInterval('P1Y3M')); // interval of 1 year 3 months added
echo $date1->format('Y-M-d'); //  Output is 2018-Apr-23

In case of date object created using DateTimeImmutable after adding the interval the original value never changes.

Example: Creating DateTimeImmutable in Different Time Zones

$date = new DateTimeImmutable('now', new DateTimeZone('America/New_York'));
echo $date->format('Y-m-d H:i:s');

Example: Handling Date Modifications

$date = new DateTimeImmutable('2023-12-25');
$newDate = $date->modify('+1 day');
echo $date->format('Y-m-d');  // Output: 2023-12-25
echo $newDate->format('Y-m-d');  // Output: 2023-12-26

Using today's date

$date = new DateTimeImmutable('now');
$newDate = $date->modify('+1 day');
echo $date->format('Y-m-d : H:i:s').'<br>';  
echo $newDate->format('Y-m-d : H:i:s');

Output

2026-09-30 : 02:47:46
2026-10-01 : 02:47:46

Using setDate()

$today = new  DateTimeImmutable();
echo $today->format('Y-m-d ').'<br>';
$changed = $today->setDate(2025, 11, 13);
echo $changed->format('Y-m-d');

Output

2026-09-30 
2025-11-13

PHP Date Functions setDate() : Set date for date object Timestamp in PHP Displaying calendar for selection of date by user

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.

About the author Watch on YouTube

Connect:

Subscribe to our YouTube Channel here