解决方法
来自GregorianCalendar的文档：
GregorianCalendar is a hybrid calendar that supports both the Julian
and Gregorian calendar systems with the support of a single
discontinuity,which corresponds by default to the Gregorian date when
the Gregorian calendar was instituted (October 15,1582 in some
countries,later in others). The cutover date may be changed by the
caller by calling setGregorianChange().
使用setGregorianChange更改它.
public void setGregorianChange(Date date) Sets the GregorianCalendar change date. This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15,1582 (Gregorian). PrevIoUs to this,dates will be in the Julian calendar. To obtain a pure Julian calendar,set the change date to Date(Long.MAX_VALUE). To obtain a pure Gregorian calendar,set the change date to Date(Long.MIN_VALUE).
