The title of your query and the question asked in the body seem to be different questions. I'm not sure I know exactly what you're asking, but I believe you will find the answer you are looking for in the following article:
NI Developer Zone: LabVIEW RT Configuring HardwareIn particular, take a look at the example code entitled, "Setting the System Date and Time". One thing to keep in mind is that if you are using "Get Date/Time In Seconds", this timestamp will fall behind if you are running any time-critical code. This is because your time-critical code actually starves the interrupt which keeps OS time. The tick count VI does work
properly, however. So your best bet if you need actual system time is to set the time with the above linked article, and then get both the system time AND a tick count from the same point in time. Do all that before your time-critical code begins. Then throughout your program you can get a tick count and calculate the actual current time based on the initial tick count and initial system time.
