Essentially the title. From experience with the French Revolution, different calendars and dating systems become agonizing. How was it possible for Western historians to convert ancient and even contemporary dates into something the Western audience could comparably understand?
More can be written, but you might like to see the FAQ section "How did the world agree on what year it is?" . For China in particular, I see "How do humans really know what year it is? What historical events started us from BCE to CE?" by [deleted] and "What happened 2012 years ago, when the date changed from BCE to CE?" by /u/Algernon_Asimov .
This is not to discourage discussion. More questions, data, and debate are welcome.