Entries live on your iPhone and sync through your own private iCloud. We cannot read them. There is no account, no login, and no server of ours holding your year.
It comes only while the day is still empty. Write the day and the evening stays quiet.
Today's frame on the home screen, the whole year as squares, and a mark on the lock screen that opens the diary.
There is no separate code inside the app: it would be nobody's to restore.
Entries sync through your own private iCloud — the iPhone writes, the iPad shows the same year.