print ("start",os.date())
-- doing some work
print(" Conversion took " .. os.difftime(os.clock(), timestart) .. " seconds")
I do not think this is a difference between actual computation time and clock time, the machine certainly is too powerfull to spent so much time in overhead.
It really depends on what you did in "-- doing some work", I'd guess
you managed to spend some time 'outside the Lua process'.
