The following is an excerpt from "The Serpent and the Jaguar by Birgitte Rasine." For those of us used to living with the no-nonsense, business-like Gregorian calendar, it can be a bit of a stretch to integrate not only a completely different timekeeping system (260 instead of 365 days, 13-day weeks, and no specific beginning or end), but also a vastly different conception of time. The ancient Maya lived - and their descendants continue to do so today - with both ordinary an