如果要在Firestore中写入时间戳类型字段，则必须使用原生JavaScript Date对象或Firestore SDK提供的Timestamp对象。你不能用你自己的物体来模拟它。

您需要从@react-native-firebase/firestore导入FirebaseFirestoreTypes。
这就是：

import {FirebaseFirestoreTypes} from '@react-native-firebase/firestore';

...

type StateTypes = {
  created_at: FirebaseFirestoreTypes.Timestamp | null;
  updated_at: FirebaseFirestoreTypes.Timestamp | null;
}

您可以为Firebase时间戳创建io-ts编解码器

import { Timestamp } from '@firebase/firestore-types';
import * as t from 'io-ts';

为时间戳定义自定义编解码器：

const FirebaseTimestamp = new t.Type<Timestamp, { seconds: number; nanoseconds: number }, unknown>(
  'FirebaseTimestamp',
  
  // `is` checks if the input value is a Timestamp.
  (input): input is Timestamp => input instanceof Timestamp,
  
  // `validate` converts the input value to a Timestamp if possible.
  (input, context) => {
    if (input instanceof Timestamp) {
      return t.success(input);
    }
    if (typeof input === 'object' && typeof input.seconds === 'number' && typeof input.nanoseconds === 'number') {
      return t.success(new Timestamp(input.seconds, input.nanoseconds));
    }
    return t.failure(input, context);
  },
  
  // `encode` converts a Timestamp back to a plain object.
  (timestamp) => ({
    seconds: timestamp.seconds,
    nanoseconds: timestamp.nanoseconds
  })
);