What exactly is the difference between Eastern Standard Time and Pacific Standard Time? And why do they--and the 22 other global time zones--exist at all? In this fun, informative set, readers learn the answers to these questions, starting with the history of time zones that began with the American railroad lines. With content that supports social studies curricula, the main text is written especially for lower elementary readers. Colorful maps throughout the book allow readers to immediately apply the map reading and geography knowledge they've gained.