Is Uposatha on full moons or specific days?

I want to start observing Uposatha, but I'm a little unclear on what days it is. I'm finding calendars that it is the days of full moons in Sri Lanka or other countries. Should it just be celebrated on full moons then? For example, I'm in the Midwest of the USA, the full moon in September is September 6 but I'm seeing Uposatha to be August 5 on calendars. Which dates should I observe on? Also, am I correct that the eight precepts to be practiced on Uposatha are: 1. Do not take life 2. Celibacy 3. Do not speak false, no lies 4. Do not steal 5. Do not use any intoxicants 6. Only eat one meal between dawn and noon (does this need to be vegetarian to fit in with the first precept?) 7. Do not use a luxurious bed that night, so sleep on a sleeping mat on the ground Are these correct?