you want it to turn on at two different times?
from what that site says it seems that there is only a grey clip (how many clips are there? so that grey clip will keep the light on for 15mins and then it will turn back off.
so try this, set the current time by putting it next to the solid triangle. set the grey clip on 8a and another on at 5pm and rotate the dial to speed the time up and see if the lights go on and off and for how long (15mins? if so add additional clips to the desired length).