In English, we generally recall important turning points in terms of where they unfolded. Simple place names conjure up entire historical epochs. "Pearl Harbor" marks the American entrance into the Second World War and the global struggle against fascism. "Bandung," the conference in of newly independent African and Asian nations that pledged to stand together in 1955 against imperialism and Cold War division. And then, of course, there is "Tian'anmen." It is doubtful that mention of the square here in China would, by itself, raise any eyebrows. But try "6-4" (六四) and you are can expect quite a different reaction. 

The difference stems from the convention in Chinese to refer to politically significant episodes in China's post-dynastic history by date (rather than place), using a truncated month-day pattern. Those with passing familiarity with modern Chinese history are likely to have come across this pattern directly transliterated in reference to major political movements, for example May Fourth (五四) or May Thirtieth (五卅). If you have spent time in mainland China you may recognize March Eighth (三八) as International Women's Day or October First (十一) as National Day. If your travels have taken you to Taiwan, you might have encountered February Twenty-eighth (二二八), a shorthand for the Guomindang's 1947 massacre of native Taiwanese, or October Tenth (双十), an alternate National Day for a government that traces its origins to the uprising that toppled China's last dynasty, the Xinhai Revolution (辛亥革命). 

In logical, if Anglophone, fashion, I had long assumed that "Xinhai" was a place name. However, yesterday I was introduced to the sixty-year naming cycle often used to reference terms in the late Qing period. This "sexagesimal" system, known in Chinese as ganzhi (干支), combines the ten heavenly stems (天干) with the twelve earthly branches (地支). The system produces a unique name for each year in the cycle. A few of the better-known events whose Chinese names derive from this system include the 1894-95 Sino-Japanese War (甲申战争), the Hundred Days of Reform of 1898 (戊戌变法), the Boxer Uprising in 1900 (庚子事变), the Boxer Protocol the following year (辛丑条约), and of course the Xinhai Revolution in 1911. Although difficult to represent visually with any elegance, I have attempted to illustrate below (click to enlarge). 

There are some limitations and exceptions to these rules. Natural disasters, as "non-political" events, might be recalled by either the place or time they occurred. For example, the 2008 Wenchuan Earthquake is known both as May Twelfth (五一二) and Wenchuan (汶川). The last big earthquake in Tangshan is similarly termed both July Twenty-seventh (二二七) and Tangshan (唐山). Simply on the basis of my own impression, I believe in both cases there is a slight preference for place over time. In addition, even highly political events sometimes take on more than one moniker. Just as the Xinhai Revolution can described in English as the Wuchang Uprising, the same (武昌起义) can be used in Chinese, especially when referencing to the initial mutiny as distinct from the overall movement to overthrow the Qing.

Still, these two methods are useful to locate sources that might reference particular historical events by what might at first be unfamiliar. Now I know to stop scanning the map for Xinhai and to ask about "Double-Twelve" (双十二事变) rather than the Xi'an Incident.