I recently added a package to my Laravel 4 site and now anything that uses Eloquent (or at least Eloquent with any reference to date/time) is showing a 500 error that states:
Class 'Carbon\Carbon' Not Found.
I tried running
composer install
composer update
composer dump-autoload
Yes, it can work as @oli-folkerd 's answer. However, as seen in Laracasts (Laravel 5 Fundamentals series Video 10 "forms" min 16:55), almost in top of your ControllerClass php file, just add the following (or import the class if your php editor allows you do so):
use Carbon\Carbon;
Now you can simply use Carbon
$input['published_at'] = Carbon::now();
without having to add Carbon\