src/Services/QueuedJobService.php
public function startJob($jobDescriptor, $startAfter = null)
    {
        if ($startAfter && strtotime($startAfter) > DBDatetime::now()->getTimestamp()) {
            $this->queueHandler->scheduleJob($jobDescriptor, $startAfter);
        } else {
            // immediately start it on the queue, however that works
            $this->queueHandler->startJobOnQueue($jobDescriptor);
        }
    }
public function startJob($jobDescriptor, $startAfter = null)
    {
        if ($startAfter && strtotime($startAfter) > DBDatetime::now()->getTimestamp()) {
            $this->queueHandler->scheduleJob($jobDescriptor, $startAfter);
        } else {
            // immediately start it on the queue, however that works
            $this->queueHandler->startJobOnQueue($jobDescriptor);
        }
    }
Start a job (or however the queue handler determines it should be started)

@param QueuedJobDescriptor $jobDescriptor
@param string $startAfter