TimeStamp100nSec is DateTime FileTime

The TimeStamp100nSec value of CounterSamples is in the same format you get from DateTime.ToFileTime() (or maybe DateTime.ToFileTimeUtc() in some situations, not sure).

This was not made clear to me in any documentation I could find, but some example code half-way down this page spells it out.

To go from TimeStamp100nSec to a DateTime object, use DateTime.FromFileTime(timestamp100nsec).