Creating Immutable Date and Time Values

When working with PHP, you may need to create DateTimeImmutable values and adjust them without mutation. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.

Creating Immutable Date and Time Values: This topic combines several operations. The code demonstrates the important sequence and its effect.

What Is Creating Immutable Date and Time Values in PHP?

Create DateTimeImmutable values and adjust them without mutation. This topic combines several operations. The code demonstrates the important sequence and its effect.

Syntax:

See the complete PHP example below.

Parameters and return value: The signature above identifies the arguments and return type where the API has a single call. For topic guides, follow the sequence of calls in the examples. Always distinguish a returned value from an object or variable modified by reference.

Important: Immutable objects protect against accidental mutation; they do not automatically resolve ambiguous local DST times.

Example 1: Basic Usage

This example introduces the operation with a short and predictable input.

<?php

$start = new DateTimeImmutable("2026-01-15 09:00:00", new DateTimeZone("UTC"));
echo $start->format(DATE_ATOM);

Output:

2026-01-15T09:00:00+00:00

The code focuses on the main operation. This topic combines several operations. The code demonstrates the important sequence and its effect.

Example 2: Another Case

Now compare a different input, locale, date, or option to see another part of the behavior.

<?php

$start = new DateTimeImmutable("2026-01-15", new DateTimeZone("UTC"));
$later = $start->modify("+1 week");
echo $start->format("Y-m-d") . " -> " . $later->format("Y-m-d");

Output:

2026-01-15 -> 2026-01-22

What changes? Immutable objects protect against accidental mutation; they do not automatically resolve ambiguous local DST times.

Practical Example: Applying It in an Application

Use the following separate example as a starting point for a small application task. Check any extension or environment requirements below before running it.

<?php

$meeting = new DateTimeImmutable("2026-01-15 09:00:00", new DateTimeZone("Europe/London"));
$participants = ["America/New_York", "Asia/Tokyo"];
foreach ($participants as $zoneId) {
    echo $zoneId . ": " . $meeting->setTimezone(new DateTimeZone($zoneId))->format("Y-m-d H:i") . PHP_EOL;
}

Output:

America/New_York: 2026-01-15 04:00
Asia/Tokyo: 2026-01-15 18:00

The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. This topic combines several operations. The code demonstrates the important sequence and its effect.

Important Behavior and Edge Cases

• Core behavior: This topic combines several operations. The code demonstrates the important sequence and its effect.
• Inputs and results: Immutable objects protect against accidental mutation; they do not automatically resolve ambiguous local DST times.
• Alternatives: DateTime is mutable; DateTimeImmutable returns new values when adjusted.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Creating Immutable Date and Time Values helps you create DateTimeImmutable values and adjust them without mutation.
• This topic combines several operations. The code demonstrates the important sequence and its effect.
• Immutable objects protect against accidental mutation; they do not automatically resolve ambiguous local DST times.

Use Creating Immutable Date and Time Values when you need to create DateTimeImmutable values and adjust them without mutation. Start with the first example, compare the second, and adapt the practical example to your inputs. Confirm the return value and environment requirements before adding it to production code.