设计并实现了一套功能是一个简单的日期计算器，考虑到跨越年。

The Gregorian Calendar was first instituted in 1582, but as you might imagine, it took time for it be used worldwide. The last conversion took place in 1918, and even today some countries follow a variant calendar. For this project assume that the rules of the calendar have been applied without correction from the present day back to 1 Jan 1600. As such, be careful when comparing your results to other date calculators that may be taking those historical discrepancies into account.