Light Sensor used for sleep mode

Does anyone know how to use a light sensor to put an Arduino to sleep when it is dark then wake it up when it is light??????

I have a light sensor (Photoresistor) through a transistor that is connected to my Arduino when it is dark the line goes high and low when it is light.

In the sleep sketch I need to send a logic low for only a second. Telling it it is dark out side. and putting it to sleep. Then when it is light out waking it back up with another low on another pin Is there a circuit that can hold that input pin low for a short amount of time then put it back high? Then do the same when it is light?

Thanks in advance,

Randy