Your answers to this question involve doing the math as to how many years each period lasted. So the order goes as follows:
- 221 B.C - 207 B.C (= 14 years)
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1368 A.D - 1644 A.D (= 276 years)
- 618 A.D - 907 A.D (= 289 years)
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960 A.D - 1279 A.D (= 319 years)
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1766 B.C - 1122 B.C (= 644 years)
The dating system used is the traditional one based on the approximate year of the birth of Jesus Christ, which is how the Western world (influenced by Christianity) typically has dated its calendars. "BC" stands for "Before Christ," and the years count from his approximate birth year backwards. "AD" stands for "Anno Domini" - Latin for "In the Year of our Lord." The years count forward from the time of Christ's birth.
