I find that most photocells turn on when they are first powered up. I don't know if that is a built in "test" feature, or just the nature of the circuit.
The way I usually hook them up together is to put the photocell first in the circuit, then to the timer, then to the lamp circuit.
Of course, you have to use a two-pole timer so you can power the clock seperately from a constant power source, or else your clock will only tick when the photocell is on. Don't want that.
