If you are logged into the desktop client, calls are presented to the desktop user irrespective of the call routing hours.

To avoid ringing on the desktop client, Do Not Disturb needs to be activated from the Desktop Client. Do activate this, click on the Settings button in the top right hand corner and then click the button in the drop-down until it turns green.

Calls will still take 30 secs to go to the voicemail irrespective of the call routing settings.