This read-create timestamp specifies when the router itself will begin using this key to sign, or generate, its own outgoing authenticated packets. An administrator schedules it to control the exact cutover moment when the local device switches to a new outgoing key during a coordinated rotation with its peers. For example, setting this a few minutes after the corresponding StartAccept time on the peer device ensures the peer is already prepared to accept packets under the new key before this router starts sending them.