If you have a large garden lighting project we have a 300 Watt Transformer with a built in Timer and dusk Dawn sensor built in. 

We also stock a separate Dusk / Dawn Timer that can be used in combination with any Transformer from our range.

The timer in both models above works via a sensor that will sense when the light has faded,  this then switches on your lights and you can regulate how long you want them to stay on for.  This can range between 1 to 9 hours.