say what? afaik (speaking as a jew here), it's when the sun goes down. (moonrise, averaged over all time, happens at any point in the 24-hour cycle.)
possibly you're thinking of when (jewish calendar) months start?
Actually I just checked to make sure, it turns out the 3 stars thing is based on a definition by Maimonides: http://en.wikipedia.org/wiki/Jewish_calendar#Measurement_of_....
say what? afaik (speaking as a jew here), it's when the sun goes down. (moonrise, averaged over all time, happens at any point in the 24-hour cycle.)
possibly you're thinking of when (jewish calendar) months start?