How do we make calendars? This lecture explores the astronomical

origins of our calendars. We start by discussing lunar and solar

calendars and their hybrids in history and tradition (for example, the

Islamic Lunar Calendar and the Hebrew Luni-Solar Calendar), and then

describe the Julian and Gregorian Calendar reforms that attempt to align

the calendar with the seasons of the year with greater degrees of

precision. Recorded 2007 Oct 3 in 1000 McPherson Lab on the Columbus

campus of The Ohio State University.