Timers are required by code in my town. At a minimum you are allowed to use a plug-in weather-proof timer, but most people have them installed when they do the electrical work for the pump and pool.

I have a simple mechanical timer wired into my breaker box in my basement, and it went in when the electrician put in the 240v GFI breaker for the pump. It's a simple gray metal box that closes. It came with one on/off pair of timer clips (they clip to the timer clock wheel) and I bought a second pair at an electrical supply house. That way I can run the pool when the sun shines (I have solar) and again at night so I can add chems in the evening.

For the winter I remove the clips, store them in the bottom of the timer's box and switch the timer's switch to "off".

Simple. Effective. Flexible.

My only limitation is I can't do fancy programming for different days of the week.

So far it's worked perfectly for years.