You can switch the light on/off by pressing the light button (front). You can then adjust the brightness by touching the buttons (- +) at the back, which unfortunately is not possible in the dark without an additional light source.
The accuracy of quartz movements is 1 - 6 minutes per year (Wikipedia), i.e. max. 1 second per day. If your day is in the a... If you wake up 1 second too late, I would talk to your therapist.