/in/foo.cc: In function 'int year(int, int)':
/in/foo.cc:6:12: warning: statement has no effect [-Wunused-value]
  for (year1; year1 < year2; year1++)
            ^
/in/foo.cc: In function 'int month(int, int)':
/in/foo.cc:26:13: warning: statement has no effect [-Wunused-value]
  for (month1; month1 < month2; month1++)
             ^
/in/foo.cc:30:11: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   else if (month1 <= 7)
           ^
/in/foo.cc:35:6: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   if (month1 > 7)
      ^