Share 'New Moon Sighting Affects Holiday Observances'

Something that is new to me this year is learning about how the observances of some holidays depend on the sighting of the new moon. I am curious to learn more about this because there seem to be staunch supporters from both ends of the spectrum. Also, then, does the observance of Shabbat also depend upon the sighting of the new moon, counting every 7th day from the sighting (meaning it would s...