eyebe,
If you just want to know the current day of the week, use the LabVIEW "Get Date/Time String" function and use Long format, then parse out the day of the week. Or, an easier way would be to use the "Get Date/Time in Seconds" wired into the "Format Date/Time String" with "%A wired to the format string.
If you want either for a specific time, you will have to translate the date/time you want to seconds since 1/1/1904 and input it into either function above.
Good luck