India’s single time-zone has been the subject of much debate over the years, with populations in the northeast demanding a separate time zone given how wide the country is.

The groundwork for a system of global time zones was laid at the International Meridian Conference of 1884. But it took several decades to be adopted around the world.

Tennessee is split between the Eastern and Central time zones. Prior to 1947, all of Tennessee observed Central time. Fourteen other states also observe multiple time zones. Eastern or Central ...