When using *Visual Studio 2008, x64, windows 7 *boost release 1.45 *Debug DLL (linked against static C runtime, /MTd) loaded/unloaded by Host application using release C runtime (debug version not avaiable!). *calling "second_clock::local_time()", as in date_time examples Deallocation problems occur when dll is unloaded. Most likely release runtime tries to free debug heap block (as far as i can tell at first inspection). The problem also occurs by calling localtime on its own: time_t tnow; time(&tnow); struct tm *time_local= localtime(&tnow); // use time_local... the following code, where "tm" is stored in local data segment, so no problem occurs, unfortunately highly unportable code: static __time64_t tnow; _time64(&tnow); static struct tm time_local; _localtime64_s(&time_local, &tnow); // use time_local... greetings mike