My digital in-wall electric timer will only work with a single pole configuration. My wiring currently has 2 switches/poles. The simplest option is screwing in an electric eye automatic light control at each of 3 outdoor lights.
Any way you like.
- Connect your in-wall timer to a relay with a 1-pole coil that controls two poles.
- Replace your timer with a two-pole timer.
To me, either of those are "simpler" than anything having to be done to three separate locations...but none of it is very complex.
- Add photosensors.
- Replace the lights with fixtures that have built-in sensors (if they are not currently LED light fixtures, that's one more reason to consider this approach.)
- depending why you have them and what purpose they are serving, use motion sensors instead of photosensors so the lights are only on when needed. Lower electric bill and less light pollution.