In this episode we discuss the evolution of the modern Gregorian calendar, as well as the engineering developments necessary to create modern clocks. Dan McGinnis returns as guest.   Thanks to Mike and Donna Bleskie, Ian Davis, Perry, Kimberlyn Crowe, Levent Kemal Sadikoglu, Russ Mangum, and more for supporting the show! If you’d like to do the same, please visit http://www.patreon.com/hi101. Paypal: paypal.me/hi101 Ko-fi: ko-fi.com/hipodcast