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

You can then use Chronos:

<?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.

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

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