Chronos focuses on providing immutable date/datetime objects. Immutable objects help ensure that datetime objects aren't accidentally modified, keeping data more predictable.

Installing with composer:

$ composer require cakephp/chronos

For details on the (minimum/maximum) PHP version see version map.

<?php
require 'vendor/autoload.php';

use Cake\Chronos\Chronos;

printf("Now: %s", Chronos::now());

Chronos was originally compatible with Carbon but has diverged and no longer extends the PHP DateTime and DateTimeImmutable classes.

Immutable objects have a number of advantages:

1. Using immutable objects is always free of side-effects.
2. Dates and times don't accidentally change underneath other parts of your code.

With those benefits in mind, there are a few things you need to keep in mind when modifying immutable objects:

// This will lose modifications
$date = new Chronos('2015-10-21 16:29:00');
$date->modify('+2 hours');

// This will keep modifications
$date = new Chronos('2015-10-21 16:29:00');
$date = $date->modify('+2 hours');

PHP only offers datetime objects as part of the native extensions. Chronos adds a number of conveniences to the traditional DateTime object and introduces a ChronosDate object. ChronosDate instances their time frozen to 00:00:00 and the timezone set to the server default timezone. This makes them ideal when working with calendar dates as the time components will always match.

use Cake\Chronos\ChronosDate;

$today = new ChronosDate();
echo $today;
// Outputs '2015-10-21'

echo $today->modify('+3 hours');
// Outputs '2015-10-21'

Like instances of Chronos, ChronosDate objects are also immutable.

When you need to work with just times (without dates), use ChronosTime:

use Cake\Chronos\ChronosTime;

$time = new ChronosTime('14:30:00');
echo $time->format('g:i A'); // 2:30 PM

// Create from components
$time = ChronosTime::create(14, 30, 0);

// Arithmetic
$later = $time->addHours(2)->addMinutes(15);

ChronosTime is useful for recurring schedules, business hours, or any scenario where the date is irrelevant.

Chronos provides setTestNow() to freeze time during testing:

use Cake\Chronos\Chronos;

// Freeze time for predictable tests
Chronos::setTestNow('2024-01-15 10:00:00');

$now = Chronos::now(); // Always 2024-01-15 10:00:00

// Reset to real time
Chronos::setTestNow(null);

For dependency injection, use ClockFactory which implements PSR-20:

use Cake\Chronos\ClockFactory;

$clock = new ClockFactory('UTC');
$now = $clock->now(); // Returns Chronos instance

// In your service
class OrderService
{
    public function __construct(private ClockInterface $clock) {}

    public function createOrder(): Order
    {
        return new Order(createdAt: $this->clock->now());
    }
}

A more descriptive documentation can be found at book.cakephp.org/chronos/3/.

API documentation can be found on api.cakephp.org/chronos.