Calendars from the Sky Questions Questions based on the Web site about calendars. (http://webexhibits.org/calendars/index.html) Tools Name:  What are calendars normally based on? What is the length of a tropical year? What is a synodic month and what is its length? About how often does a year come along that that the phases of the moon falls on the same dates? What are the two main types of "Christian Calendars"? What years are leap years? What day of the week was August 2, 1953? How did Romans number days? What is the Indiction and how is it calculated? What is a Lunisolar Calendar? Survey created by: Michelle Warthan