Probably nothing, but interesting correlation nonetheless:
At rallies when POTUS wasn't a shadow POTUS: "Promises Made, Promises Kept"
Titles of books "authored" by Joe Biden:
Promises to Keep (©2007)
Promise Me, Dad (©2017)
Clear speculation: all signs pointed to Biden 2020.
Unusual:
Amazon shows the 2008 paperback edition being published on January 1, 1672.
Board won't let me post the amazon link because it's suspected of being spam. Go to Amazon and type Promises to keep joe biden if you need the source.