Microsoft graph api MS Graph lastModifiedDateTime和SharePoint REST API TimeLastModified对于同一文件是不同的

我使用Web界面将文件上载到用户的OneDrive，然后使用两个API获取文件信息：MS Graph API和SharePoint REST API

对于MS Graph API，我使用了以下端点：

https://graph.microsoft.com/v1.0/drives/b{drive-id}/items/{item-id}

https://*my.sharepoint.com/personal/*/_api/Web/GetFileByServerRelativePath(decodedurl='*/test.psd')

我得到的回答是：

{
    ***
    "createdDateTime": "2019-12-09T15:03:52Z",
    "eTag": "\"{9E8670D4-185F-4E8D-B2E5-61819E769BC3},2\"",
    "lastModifiedDateTime": "2019-12-09T15:04:12Z",
    "name": "test.psd",
    "cTag": "\"c:{9E8670D4-185F-4E8D-B2E5-61819E769BC3},2\"",
    "size": 56783858,

    "lastModifiedBy": {
        "user": {
            "email": "batman@keepitdev02.onmicrosoft.com",
            "id": "6e14d588-63db-46e4-b70d-0f00050dafa4",
            "displayName": "Batman"
        }
    },
    "fileSystemInfo": {
        "createdDateTime": "2019-12-09T15:03:52Z",
        "lastModifiedDateTime": "2019-12-09T15:04:12Z"
    },
    ***
}

对于SharePoint REST API，我使用了端点：

https://graph.microsoft.com/v1.0/drives/b{drive-id}/items/{item-id}

https://*my.sharepoint.com/personal/*/_api/Web/GetFileByServerRelativePath(decodedurl='*/test.psd')

我得到的答复是：

---

---

返回的API修改时间为：

• MS图：2019-12-09T15:04:12Z

• SharePoint REST API:2019-12-09T15:04:11Z
  正如你所看到的，它们相差1秒。有人能解释为什么我会看到这样的差异吗