Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires psr/clock-implementation *, it could not be found in any version, but the following packages provide it: - nesbot/carbon An API extension for DateTime that supports 281 different languages. - symfony/clock Decouples applications from the system clock - lcobucci/clock Yet another clock abstraction - beste/clock A collection of Clock implementations - cakephp/chronos A simple API extension for DateTime. - symfony/symfony The Symfony PHP framework - eventsauce/clock Consume time from a Clock - ergebnis/clock Provides abstractions of a clock. - okvpn/clock-lts Adding support for a wider range of PHP versions to lcobucci/clock - lendable/clock Clock Abstraction - orisai/clock Provides current time for runtime and controllable time for testing - arokettu/system-clock The smallest PSR-20 implementation (PHP 7.0 and later) - cerpus/edlib-resource-kit-laravel Integrate Edlib Resource Kit with Laravel - arnapou/psr-clock Library - PSR-20. - arokettu/clock PSR-20 Implementation ... and 36 more. Consider requiring one of these to satisfy the psr/clock-implementation requirement. Potential causes: - A typo in the package name - The package is not available in a stable-enough version according to your minimum-stability setting see <https://getcomposer.org/doc/04-schema.md#minimum-stability> for more details. - It's a private package and you forgot to add a custom repository to find it Read <https://getcomposer.org/doc/articles/troubleshooting.md> for further common problems.