Class 'Locale' not found

If, with the constructor of the Time class, all parameters are passed explicitly, then most likely the call to the Locale :: getDefault () function due to which an error occurs can be avoided.

PHP Code:

class Time {
public function __construct(string $time = null, $timezone = null, string $locale = null)
    {
        // If no locale was provided, grab it from Locale (set by IncomingRequest for web requests)
        $this->locale = ! empty($locale) ? $locale : Locale::getDefault();
} 


What I should to do now?