Even if you long ago got the basic gist behind Daylight Saving Time—tweaking the clock twice a year so that our routinized, Industrial-Age workday aligns better with sunlit hours—you will amost certainly learn something from the six-and-a-half-minute video below, which not only explains the idea of DST, but also details its history and its various quirks—including the one illustrated above: While Arizona is one of two U.S. states that does not observe DST, the Navajo Nation does observe it, and the Hopi Nation, meanwhile, does not; hence, that blue and orange mishmash of Sun Belt timezones.
The video was produced by C.G.P. Grey, who has made a series of witty YouTube explanations for things ranging from coffee to copyright to the electoral college. Most are about five minutes long, and much funnier (and more informative) than your average Wikipedia entry. You can find them all on Grey’s YouTube page.