...If you're using Symfony, you may check our Symfony configuration and best-practices recommendations. Each version of Laravel has its own range of Carbon compatibility, you have to take 2.42.0 as the real used version, then pick an alias among versions Laravel supports. You may have other dependencies with other Carbon restrictions. To be sure an alias will be compatible with all of your current dependencies, you can choose the version of Carbon you have before upgrading to Carbon 2. The library also provides CarbonInterface interface extends DateTimeInterface and JsonSerializable, CarbonInterval class extends DateInterval, CarbonTimeZone class extends DateTimeZone and CarbonPeriod class polyfills DatePeriod.