Carbon vs DateTimeImmutable

Carbon wraps DateTime with a friendlier API: now()->addDays(5)->startOfMonth(). The catch is mutability — operations modify the instance.

For new code, prefer CarbonImmutable (or plain DateTimeImmutable). Mutation bugs hide in plain sight when the same instance is referenced from multiple places.

Laravel 10 standardised on immutable Carbon under the hood; new projects get this for free.