/* Simple program that uses the gregorian calendar to progress by exactly * one month, regardless of how many days are in that month. * * This method can be used as an alternative to iterators */ #include "boost/date_time/gregorian/gregorian.hpp" #include <iostream> int main() { using namespace boost::gregorian; 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; } /* Copyright 2001-2005: CrystalClear Software, Inc * http://www.crystalclearsoftware.com * * Subject to the Boost Software License, Version 1.0. * (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) */