I lost the inatructions: how so I set it up for e.g 8 hours? If I select 8 hours, nothing happens ... thanks.

Hello Timberjacks! You simply ROTATE the TIME DIAL to the 8 hour mark and the lights SHOULD stay on for 8 hours after the Sun goes down to ACTIVATE the Sensor Switch. If it WORKS on ALL the other TIME Slots then this Timer Plug might be defective. I usually only have my lights on for 6 hours and really have never USED the 8 hour feature. If it doesn't work then return it to the store

when you set the dial to 8, the timer will turn the lights on at dark and then turn them off 8 hours later. The photo-cell triggers the timer (on at dark, off at light) unless you set 2,4,6,8 hours, which indicates hours after dark to shut off.