math.txt

$ bc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
1455664279688 - 1455664279541
147

results.txt

$ node timings.js | ts '[%Y-%m-%d %H:%M:%.S]'
[2016-02-16 15:11:19.550597] starting 1455664279541
[2016-02-16 15:11:19.688965] after 200ms 1455664279688

timings.js

console.log('starting', new Date().getTime());
setTimeout(function() {
  console.log('after 200ms', new Date().getTime());
}, 200);