Milliseconds to timestamp

to_timestamp.rb

# based in http://stackoverflow.com/a/10874157
def to_timestamp(x)
  y = 60*60*1000
  h = x/y
  m = (x-(h*y))/(y/60)
  s = (x-(h*y)-(m*(y/60)))/1000
  mi = x-(h*y)-(m*(y/60))-(s*1000)

  string = "#{h.to_s.rjust(2, '0')}:#{m.to_s.rjust(2, '0')}:#{s.to_s.rjust(2, '0')},#{mi.to_s.rjust(3, '0')}"
end