This time last year...........

Not really, JJB as it will only be in This month or the previous month. Anything that happened before then can wait until next year.
There may be a trip to B&M later today as they have some £1.50 notebooks in various designs. I'll see how many different ones they have - don't want duplicates as that would be confusing. https://www.bmstores.co.uk/search?sortBy...c&query=A5

Or one big book with dividers?

Discussing this with Paul he did raise the query about the differing seasons not conforming to the same month each year.  I'm toying with a fat book with sections for each  type of plant for the veg patch.  Yes I have the spreadsheet for dates etc, but as you say you can ramble better in a book, plus it comes up the patch with me..

Just look  what you've started!