I'm experiencing a problem using custom formatting of fractional seconds. const std::string date_string = "2006 Jun 01 999000 23.59.59"; const std::string format_string = "%Y %b %d %f %H.%M.%S"; When using a time_facet together with the "%f" flag, I get a correct output containing a 6-digit number in place of the fractional part. However, using a time_input_facet together with the "%f" flag, I cannot get a correct ptime from an input using the same format as the above example. The problem is twofold : 1) First, the input facet expects a leading '.' otherwise, it parses a special value and fails. [see time_facet.hpp(1035-1049)] This is not the case in an output facet. 2) Second, even if I include a leading dot, the space after the fractional seconds is not consumed, and the parsing of the remainder fails. This means that I need to add an extra space to the input format string. Here is a sample program: --------- #include <cassert> #include Using namespace boost; ... posix_time::ptime time; const std::string input_format = "%Y %b %d %f %H.%M.%S"; // formats are const std::string output_format = "%Y %b %d .%f %H.%M.%S"; // not symmetric const std::string input_date_string = "2006 Jun 01 .999000 23.59.59"; std::string output_date_string; { posix_time::time_input_facet* input_facet = new posix_time::time_input_facet(input_format.c_str()); std::istringstream in(input_date_string); in.imbue(std::locale(std::locale::classic(), input_facet)); in >> time; } { posix_time::time_facet* output_facet = new posix_time::time_facet(output_format.c_str()); std::ostringstream out; out.imbue(std::locale(std::locale::classic(), output_facet)); out << time; output_date_string = out.str(); } assert( output_date_string == input_date_string ); --------- Am I missing something ? Thanks for your help. Maxime LABELLE.