hi. #include <boost/date_time/posix_time/ptime.hpp> int main() { boost::posix_time::ptime x(boost::date_time::not_a_date_time); } # g++ --version 2.95.4 #g++ -Wall -c foo.cpp -Iboost_1_31_0 (compiling into cache) foo.cpp: In function `int main()': foo.cpp:5: no matching function for call to `boost::posix_time::ptime::ptime (boost::date_time::special_values)' boost/boost/date_time/posix_time/ptime.hpp:39: candidates are: boost::posix_time::ptime::ptime(boost::gregorian::date, boost::posix_time::time_duration) boost/boost/date_time/posix_time/ptime.hpp:42: boost::posix_time::ptime::ptime(boost::gregorian::date) boost/boost/date_time/posix_time/ptime.hpp:45: boost::posix_time::ptime::ptime(const boost::posix_time::int64_time_rep &) boost/boost/date_time/posix_time/ptime.hpp:48: boost::posix_time::ptime::ptime(const boost::posix_time::ptime &) foo.cpp:5: warning: unused variable `class boost::posix_time::ptime x' -- Erik Thiele