Startdates	Enddates	Location	Total Affected
02/08/2009	08/08/2009	Chongqing	50000
01/08/2009	05/08/2009	shanghai
11/11/2009	14/11/2009	Anhui, Hubei provinces	1197799
09/11/2009	12/11/2009	Shaanxi, Hebei, Shijiazhu ...	10000096

如何进行时间段聚类？即根据开始结束的时间进行聚类呢，每隔一周聚为一类呢？