The Ramadan fast may start tomorrow morning, or it may start on Saturday morning. The astronomic calculations suggest that it will be Saturday, but it could be Friday. It may start on different dates in different parts of the world, depending on the moonsighting and what rules people follow about it.
I go by the Islamic Society of North America's decision on moonsighting. We'll see if the new crescent moon is sighted tonight in North America, inshallah.