Hello I think I found a configuration issue while building boost 1.32.0 with VC .Net 2003 (VC71) using STLport 5.0 beta (latest from cvs STLPORT_5_0 branch). Maybe someone already notive this problem but the latest boost CVS version still show it. With the STLport lib the macro configuration is : - BOOST_NO_INTRINSIC_WCHAR_T defined - BOOST_NO_STD_WSTRING _not_ defined, wstring are supported Thanks to the BOOST_NO_STD_WSTRING macro the date_time lib instanciate code for wstring specific type. For instance in libs/date_time/src/gregorian/greg_month.cpp you will find a block of code in a #ifndef BOOST_NO_STD_WSTRING block. The date_time lib use the lexical_cast tool. But the lexical_cast tool do not care about BOOST_NO_STD_WSTRING and rather check, among other macros, BOOST_NO_INTRINSIC_WCHAR_T and so do not grant the necessary specialization for wchar_t and wstring. The error message is then something like: D:\boost_1_32_0\boost/lexical_cast.hpp(137): error: no operator "<<" matches these operands operand types are: std::basic_stringstream<wchar_t, std::char_traits<wchar_t> , std::allocator<wchar_t> > << const std::basic_string<char, std::char_traits<char> , std::allocator<char>> return stream << input; Sorry for not having the accurate message but I have the compiler on an other computer. I see 2 possible solutions to this problem: - concider that there is no wstring support if there is no intrinsic wchar_t support. - make lexical_cast less strict and do not require intrinsic wchar_t support. Bests