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

I really would suggest a spreadsheet though there is no entry in my dictionary for the word so must be quite new.

Doesn't cost anything
could use a tab for each year like me or month as you say or you could have a different one for each main crop.
You could fill it/them in when you go on g&g in the evening

Different crops can be recorded in different ways. for me tomatoes are at the top with the varieties/sowing dates/germination/potting on (or grafting)/planting out/notes. Then I record date/variety/weight picked. It does all the adding up and taking away for me.

The only problem is where it says recorded above doesn't always happen. I might look for when I sowed parsnips last year and find the date sown blank - but that can happen in a written diary and is is not as easy to search.

I do have one other spreadsheet for financial stuff as I have a few small pensions and the tax man was always wanting more from me than was due. (S)he was always more optimistic about my income than what I got. This has sorted now but it is still useful to keep a tab on different kinds of expenditure (I haven't got a column for gardening).