DCDevice last_update_time issue

We are currently experiencing an unexpected issue with the DeviceCheck query_two_bits endpoint. According to the official documentation (Accessing and Modifying Per-Device Data), the last_update_time field should represent the month and year when the bits were last modified.

The Issue: For several specific device tokens, our server is receiving a last_update_time value that is set in the future.

Current Date: April 2026

Returned last_update_time: 2026-12 (December 2026)

Here is a response:

{
	"body": "{\"bit0\":false,\"bit1\":true,\"last_update_time\":\"2026-12\"}",
	"headers": {
		"Server": ["Apple"],
		"Date": ["Thu, 02 Apr 2026 06:05:23 GMT"],
		"Content-Type": ["application/json; charset=UTF-8"],
		"Transfer-Encoding": ["chunked"],
		"Connection": ["keep-alive"],
		"X-Apple-Request-UUID": ["53e16c38-d9f7-4d58-a354-ce07a4eaa35b"],
		"X-Responding-Instance": ["af-bit-store-56b5b6b478-k8hnh"],
		"Strict-Transport-Security": ["max-age=31536000; includeSubdomains"],
		"X-Frame-Options": ["SAMEORIGIN"],
		"X-Content-Type-Options": ["nosniff"],
		"X-XSS-Protection": ["1; mode=block"]
	},
	"statusCode": "OK",
	"statusCodeValue": 200
}

Technical Details:

Endpoint: https://api.development.devicecheck.apple.com/v1/query_two_bits (also occurring in Production)

Response Body Example:

JSON

{
  "bit0": true,
  "bit1": false,
  "last_update_time": "2026-12"
}

Observations: This occurs even when our server has not sent an update_two_bits request for that specific device in the current month.

Questions:

Is there a known issue with the timestamp synchronization or regional database propagation for DeviceCheck?

Does the last_update_time field ever represent an expiration date or any value other than the "last modified" month?

Best regards,