This is because the part night lights are linked to ‘solar time’ rather that the standard time that is shown on a clock.
The difference between solar time and the time on your clocks and watches varies throughout the course of a year. What this means for your street lights is that the time they will switch on varies with this, from as early as 05:44 on 03 November to as late as 06:14 on 12 February. This same variation will repeat itself every year.