As presented in this chapter, time zones were established

a$.$ to coordinate television schedules in the $1940$s$.$

b$.$ to coordinate telegraph station time$-$stamps in the $1800s.$

c$.$ to simplify record keeping at NATO Army bases around the globe.

d$.$ to coordinate train schedules.

e$.$ to work with John Harrison's time solution for determining longitude at sea.

f$.$ D and $E$