编写一个日期类Date类，它有三个数据：Year,Month和Day。涉及的操作有给数据赋值、输出数据的值。

//Date class class Date { public: Date(int year=1990, int month=1, int day=1) { m_iYear = year; m_iMonth = month; m_iDay = day; } Date( Date date) { m_iYear = date.m_iYear ; m_iMonth = date.m_iMonth ; m_iDay = date.m_iDay ; }