What time is it? Telling time is the oldest practical application of astronomy. Today's lecture is the first of a 2-part lecture on the astronomical origins of our methods of keeping time and making calendars. This lecture reviews the divisions of the year into the solstices, equinoxes, and cross-quarter days, the division of the year into months by moon phase cycles, months into weeks, and the division of the day into hours by marking the location of the Sun in the sky Recorded 2007 Oct 2 in 1000 McPherson Lab on the Columbus campus of The Ohio State University.