I now use a small notebook, just 80 pages and pocket-sized. All entries are timestamped. When I reach the end and start a new one, I review the last one and my first entry is a list of things from the last that I still find interesting.
Just out of curiosity - what is the time stamp for?
I also keep noteboks. I have a rough idea of what months / years they span. I've never needed to know the exact date or time I had an idea. Are you trying to find out which part of the day gives you the most ideas?
Sorry, missed this. I date/timestamp everything (a) so that it also functions as a diary, and (b) as an aid to memory - sometimes seeing the time/date helps me reconjure the context of the thoughts.
Though I rarely browse through that list of ideas - a couple times a week, maybe, or when I need new ideas for content :-)