Massachusetts

Uniform time zones in this country came about in the late 19th century because the railroads needed to be able to publish and adhere to schedules for the trains. Before then each city and locality had its own local time.

During WWI and WWII "war time" was observed, essentially DST as we know it. After WWII DST was observed in a hodge-podge, with different states and localities choosing whether or not to observe it.

In 1966 a federal law was passed requiring all states to observe DST, starting and ending on the same dates. Arizona opted out after one year.

Countries closer to the equator have more nearly equal days and nights. Very northern or southern parts of the globe have longer days in the summer, very short ones in the winter, and some get six months of darkness six months of night. The sun moves from east to west, that's why the time zones are based on east/west locations, not north/south.

In the 1970's DST was fiddled with, to the great dismay of many people.

I like DST. I do think it should start a month later and end a month earlier than it does, but I'm not in charge.