History 急!

What do we mean by "written records"?
Today, most people are using the Christian calender to court time, can you name TWO other calenders used by people around th world?(除左"Before Christ[B.C.]"
& "Anno Domini[A.D.]"
Update: Which comes first?
1.Prehistoric times
2.Hong Kong was restored to China
3.Trojan War
4.The construction of the Great Wall
5. The Olympic Games in Beijing
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