/in/foo.cc: In function 'std::ostream& operator<<(std::ostream&, const Time&)':
/in/foo.cc:11:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
/in/foo.cc: In function 'std::ostream& operator<<(std::ostream&, const Date&)':
/in/foo.cc:55:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
/in/foo.cc: In member function 'll Date::operator-(Date&)':
/in/foo.cc:84:13: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    if(i%4==0&&i%100!=0||i%400==0)
       ~~~~~~^~~~~~~~~~