[Boost-users] [date_time] problem adding negative number of months

From: Guido Spahn (gspahn_at_[hidden])
Date: 2005-08-22 04:26:12

Hello,

when adding a negative number of months to a date(y, m, d), an exception 
"Month number is out of range 1..12" is raised if the resulting month m2 
belongs to a year y2 < y and m2 > m. For example

  date(2005, Jan, 1) + months(-1) fails
  date(2005, Feb, 1) + months(-1) doesn't fail
  date(2005, Feb, 1) + months(-2) fails
  date(2005, Feb, 1) + months(-12) doesn't fail
  date(2005, Feb, 1) + months(-13) doesn't fail
  date(2005, Feb, 1) + months(-14) fails

I checked it only with release 1.33 using the appended code. There is no 
problem adding or substracting any positive number of months.

Hopefully I didn't miss this topic in the mailing list archive. Thanks in 
advance,

Guido

#include <boost/date_time/gregorian/gregorian.hpp>
int
main()
{
  using namespace boost::gregorian;
  date d(2005, May, 1);
  for (long m = 0; m >= -40; --m)
  {
    try
    {
      std::cerr << d << " + (" << m << "): ";
      std::cerr << d + months(m) << std::endl;
    }
    catch (std::exception& e)
    {
      std::cerr << "FAILED: " << e.what() << std::endl;
    }
  }
  return 0;
}