How can I dim LED Christmas lights?
Not all LED's are dimmable.  The box should say if they are dimmable. Usually if they are dimmable, the instructions might say something like dimmable with standard dimmers.  If they are dimmable and you use a regular dimmer they will dim but a standard dimmer will not give you 100% dimming and might go bright to off in half a turn or slide.  Dimmers for LED's have a trim wheel that you can adjust and give you a more balanced dimmer and effect.