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

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

2025-10-14 : 03:30:31
2025-10-15 : 03:30:31

Using setDate()

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

Output

2025-10-14 
2025-10-14

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

Subhendu Mohapatra

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