code: function parse (val) {
    assert(exists(val), 'Invalid date: ' + val)
    var date = new Date(val)
    assert(!isNaN(date.valueOf()), 'Invalid date: ' + val)
    return date
  }
docs: parse date from literal
  @param  {*} val
  @throws {TypeError} If `val` is not a valid date
  @return {Date}     [description]