boost::local_time::operator-
// In header: <boost/date_time/local_time/date_duration_operators.hpp> local_date_time operator-(const local_date_time & t, const boost::gregorian::years & y);
Subtracts a years object and a local_date_time. Result will be same month and day-of-month as local_date_time unless original day was the last day of month. see date_time::years_duration for more details
