Probably the second most populous shall be GMT+1, with most of europe and large parts of Africa in. There shall be probably 800-900 million people living thereGMT +8 includes all of China, the Phillippines, Malaysia and parts of Indonesia so it's the most populous time zone in the world.
UTC -9:30 contains only the Marquesas Islands. 8,632 inhabitants at the 2007 census. Probably one of the the least populated, if not THE least populated time zone.The least populated ones must be the Pacific ones and GMT -2, where you only have Fernando de Noronha (Brazil) and some other small archipelagoes.