Why are the time zones on land so crooked?

When you cross a line between two time zones, you gain or lose an hour. It would bo very inconvenient if you had to do this to and from school or on a shopping trip from one side of town to another. The time zones on land zig zag around densely populated areas to avoid these inconveniences. Sometimes they follow a winding river or state line.

On the wide wastes of the ocean there is less need to bend the lines between the time zones. But even here they are bent to include certain island populations in the same zone.