Hi Vincent,
it depends how accurate you need to have the time information. For example, you already have the time information included as an attribute of the file (of course, with a little delay).
Anyway, record the date before and after acquiring those 600 points (use 'seconds expired since 1904' format to be easier with calculations). Assuming that between every two consecutive points the delay is the same, you can calculate a time stamp for everyone. Otherwise you have to record it separately for each point.
If something unclear, let me know labviewer@yahoo.com