Q: Hi guys, anybody can tell me when the two are celebrated and for what?
A: Besides all the technical part, Holi marks the end of Winter and Diwali starts Winter. The Monsoon insects get burnt in the lamps . Holi, you burn fire the day before, Holika, and get everyone wet the next day. Color them so they take a good bath. And ends the fear of Winter baths. So Diwali is Kartik Amavasya. End of Autumn. Oct-Nov. Holi is March- April . 22nd March 2008. Height of Spring. It is Phalgun Poornima. Your Q was why: 1 Diwali: it is a day that started when "Lord Rama" returned to Ayodhya after his exile. Ayodhya was lit up with rows of lamps. 2. Holika was a demon. She was burnt alive. That is Holi. It is the end of evil. Can give you details if you want. Is very long. There are many stories. Sure Wikipedia will also give them. But it is also a significance with weather.