Which empire was able to dramatically expand its territory due to its superior iron weapons

The Assyrian Empire did so

if you are talking about current time the answer is no

if you are talking about when the colonies were developing the answer is yes

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: