A timestamp in RFC3339 UTC "Zulu" format, with nanosecond resolution and up to nine fractional digits. Examples: "2014-10-02T15:01:23Z" and "2014-10-02T15:01:23.045123456Z".
[null,null,["Last updated 2023-10-03 UTC."],[],["Upon successful registration, the response includes the registered MSISDN and its expiration time. The MSISDN is a string representing the phone number registered for notifications. The expiration time is a timestamp in RFC3339 UTC \"Zulu\" format, detailing when the registration expires, including nanosecond resolution. This timestamp can display up to nine fractional digits, showing examples of the format.\n"]]