建立一个日期类，计算各日期间关系特殊判断 包括：①对是否是闰年进行判断；

②根据闰年判断结果，确定特殊月份2月的截止天数；

③分别对大月（31天）和小月（30天）不同月份是否到月末进行判断；

④对是否跨年进行判断。

-The date of the establishment of a category to calculate the date of the special relationship between the judge, including: ① on whether or not to be judged is a leap year　② According to judge the outcome of a leap year, the month of February to determine the particular cut-off number of days　③, respectively, of large month (31 days) and Xiaoyue ( 30 days) in different months to determine whether or not to late　④ judge on whether or not New Year.