What led to the demise of the roman empire

One of the most important reasons for the demise of the vast Roman Empire was the invasions of the barbarian tribes from the North. Rome was constantly at odds with these tribes throughout its existence but the threat became severe with the increasing migrations and invasions of these tribes after 200 AD.

Explanation:

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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: