Header <boost/itl/ptime.hpp>

namespace boost {
  namespace itl {
    template<> struct difference<boost::posix_time::ptime>;
    template<> struct size<boost::posix_time::ptime>;
    boost::posix_time::ptime operator++(boost::posix_time::ptime & x);
    boost::posix_time::ptime operator--(boost::posix_time::ptime & x);
    boost::posix_time::time_duration 
    operator++(boost::posix_time::time_duration & x);
    boost::posix_time::time_duration 
    operator--(boost::posix_time::time_duration & x);
  }
}