Over here in the UK some streetlights have part-night time switches or photocells. That means that they come on at dusk, switch off about midnight and if it still dark at 5am, they come back on. The part night photocells automatically calibrates itself to the time so on the first few days they operate all night then once they are calibrated they go to part night control. If there is a powercut, the photocells will need a another few days to recalibrate themselves.
Regards DP
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