The demo UTC time synchronization function 'Send_TimeSyncUTC" in file "Demo/s_ts.c" seems to miss the NPDU encoding. In comparaision in "Send_TimeSync" the NPDU is encoded there and everything seems to work fine.
Thank you for your bug report. This has now been fixed in the 0.5.4 release.
I just saw this discussion from 2009. However, this seems to contradict the report from http://sourceforge.net/p/bacnet/bugs/27/ . Is it truly fixed?
The Send_TimeSyncUTC() sends a date and time with the appropriate service encoded in the message. It does not automatically convert to UTC Time using the UTC_Offset, Local_Time, and Local_Date properties from Device object, as the http://sourceforge.net/p/bacnet/bugs/27/ requests.