Maybe this is in the wrong category but what's a date book?

A date book is a portable calendar in book form. Best way I can describe it. A lot of people use these for business or if they are very busy people, they keep a date book to keep up with daily appointments. It is larger than a pocket calendar, but some people call those date books.

Hope this helps.

Thanks. I appreciate it. I always thought it was an agenda. Any idea of when it was invented?

Not a clue, my friend. I can tell you that I know they have been manufactured for at least 50 years but I suspect they are much older than that.

BTW, an agenda is, to put it simply, a "to do" list.