Something like this: http://www.spectracomcorp.com/Desktopmodules/Bring2Mind/DMX/Download.aspx?EntryId=287&PortalId=0 http://www.spectracomcorp.com/Desktopmodu

Something like this: http://www.spectracomcorp.com/Desktopmodules/Bring2Mind/DMX/Download.aspx?EntryId=287&PortalId=0 http://www.spectracomcorp.com/Desktopmodules/Bring2Mind/DMX/... The units are a bit confusing but the accuracy still translates down to a handful of nanoseconds per month, I believe.