class ActiveModel::Type::DateTime

def cast_value(value)
  return apply_seconds_precision(value) unless value.is_a?(::String)
  return if value.empty?
  fast_string_to_time(value) || fallback_string_to_time(value)
end

def fallback_string_to_time(string)
  time_hash = ::Date._parse(string)
  time_hash[:sec_fraction] = microseconds(time_hash)
  new_time(*time_hash.values_at(:year, :mon, :mday, :hour, :min, :sec, :sec_fraction, :offset))
end

def microseconds(time)
  time[:sec_fraction] ? (time[:sec_fraction] * 1_000_000).to_i : 0
end

def type
  :datetime
end

def value_from_multiparameter_assignment(values_hash)
  missing_parameter = (1..3).detect { |key| !values_hash.key?(key) }
  if missing_parameter
    raise ArgumentError, missing_parameter
  end
  super
end