Pretty。

gistfile1.coffee

module.exports = (time) ->
  elapse =
    if time instanceof Date
      time.getTime() - Date.now()
    else if typeof time == "number"
      time - Date.now()
    else
      console.warn "Given a invalid date type(\"#{typeof time}\") arguments. expected date type is Date or Number."
      ""
  
  if elapse < 10.sec
    return "たった今"
  if elapse < 30.sec
    return "30秒前"
  if elapse <  1.hour
    return "#{Math.floor(elapse / 1.min)}分前"
  if elapse <  1.day
    return "#{Math.floor(elapse / 1.hour)}時間前"
  if elapse <  1.week
    return "#{Math.floor(elapse / 1.day)}日前"
  if elapse <  1.year
    return "x月x日"
  
  return "x年x月x日"