CakePHP Chronos
A standalone DateTime library originally based off of Carbon
...Immutable objects help ensure that datetime objects aren't accidentally modified keeping data more predictable. Chronos was originally compatible with Carbon but has diverged and no longer extends the PHP DateTime and DateTimeImmutable classes. 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.