Sikkim advice needed

I'm planning a trip to Sikkim and would like to include several days of trekking in my trip. Because of my work schedule there are two times of year that I can travel:

1. Between December 15 and January 20.

2. Any time between May 5 and August 30.

What is the best time for me to schedule a 2-3 week trip?

Thanks!

In December/January it is too cold, particularly if you want to do some trekking - go early May...

Go in early May to beat the start of the monsoon season!

i will also suggest you to go in early may.. dec/jan is very cold and the routes where you want to trek will be cold and it will be too much snow. it will be better if you contact a local trekking agent and plan your trek. you can also reach gangtok and check for trekking groups in different local trekking agency.