Sorry if this is a basic c++ misunderstanding on my part, but why does this compile, since there is no using in this code and to_iso_string is in namespace boost::gregorian? #include <boost/date_time/gregorian/formatters.hpp> #include <iostream> int main(int argc, char** argv) { boost::gregorian::date d(2010, 1, 1); std::cout << to_iso_string(d) << std::endl; std::cout << to_iso_extended_string(d) << std::endl; std::cout << to_simple_string(d) << std::endl; return 0; } ------------------------------ g++ to_iso_string.cpp -I../boost_1_44_0/include -L../boost_1_44_0/lib - lboost_date_time-mt Thanks Dan