typedef boost::date_time::month_functor<date> add_month;
main(){  using namespace boost::gregorian;  typedef boost::date_time::month_functor<date> add_month;  date d = day_clock::local_day();  date d2 = d + months(1);   date d3 = d - months(1);  std::cout << "Today is: " << to_simple_string(d) << ".\n"            << "One month from today will be: " << to_simple_string(d2)             << "One month ago was: " << to_simple_string(d3)            << std::endl;  std::cout << "******** Warning read this ***********************\n";  std::cout << "Be aware that adding a month is not exactly like regular numeric math.\n"            << "Addition/Subtraction of months will 'snap to the end' of a month that\n"            << "is shorter than the current month.  For example consider "            << "Jan 31, 2004 + (1 month)\n";  date d4(2004, Jan, 31);  date d5 = d4 + months(1);  std::cout << "Result is: " << to_simple_string(d5)             << std::endl;  std::cout << "\nSo what does this mean?  It means the result of adding months is order\n"            << "dependent, non-communitive, and may create problems for applications.\n"            << "Consider: \n"            << "Jan 30, 2004 + (1 month) + (1 month) != Jan 29, 2004 + (2 months)\n"            << "Why not? Because Jan 30, 2004 + 1 month is Feb 29 + 1 month is Mar 29th.\n"            << "while Jan 30, 2004 + 2 months is Mar 29th.\n"            << "All of this clears up as long as all the starting dates before the 28th of\n"            << "the month -- then all the behavior follows classical mathematical rules.\n";    return 0;}