appwrite/docs/examples/1.6.x/server-dotnet/examples/databases/update-datetime-attribute.md

using Appwrite;
using Appwrite.Models;
using Appwrite.Services;

Client client = new Client()
    .SetEndPoint("https://cloud.appwrite.io/v1") // Your API Endpoint
    .SetProject("<YOUR_PROJECT_ID>") // Your project ID
    .SetKey("<YOUR_API_KEY>"); // Your secret API key

Databases databases = new Databases(client);

AttributeDatetime result = await databases.UpdateDatetimeAttribute(
    databaseId: "<DATABASE_ID>",
    collectionId: "<COLLECTION_ID>",
    key: "",
    required: false,
    default: "",
    newKey: "" // optional
);