Like J Paul, I have been using a ledger since 2010. I am on my second notebook. I have not moved to a digital method on a computer because I don't keep one in the studio and know that I would not keep the digital method updated. Each piece I finish has their own individual serial number, that coincides with the information kept in the ledger. The information recorded also includes the dimensions, wood species, identity of the form (bowl, hollow form, etc.), any surface embellishments and color, and whether it is one that falls into a named body of work, (Soul Series, Illusions in Wood, etc). The ledger is divided by month/year.
Some months have very few (or sometimes nothing) completed. In that space, I note the reason; joint replacement/surgery, spent the month roughing work out, heavy travel month with shows and workshops. I typically only include the date/year on my work that is part of a series.
Like Paul, it has become important to people who collect my work, to know when the piece was made. When I began doing that, I did not know where my journey would take me. But I recalled David Ellsworth offering suggestions for makers who were in the early stages of that journey, especially those who were exploring their artistic side. He said, you don't know where your journey will take you but prepare for where you might end up. Keep records and hang on to some of your earlier pieces. You never know who might be interested in the earliest works of a collection. For example, I have a couple of collectors who own several of my Soul Series pieces, and they like to see the difference in progression in that body of work.