The tablature I learned from in the mid-60s (Stephan Grossman books, other Oak Publications) showed time quite clearly, in the exact same manner as standard sheet music (quarter-notes, eigths, halves, etc.) Nowadays, it seems that much of the tablature I see -- printed off the internet -- is cruder, just showing the tones (string/fret intersections) but not showing the timing, at least not very clearly.

I think this is mostly due to the difficulties of building little grid-type diagrams out of compuer keystrokes, but as more and more people get more and more familar and comfortable with this cruder form of tab, the finer approach is being forgotten. By the time we develop the technical tools to easily produce better tabs on our PCs, we may have forgotten how to do so (or forgotten that there ever was such a thing).

When I was young, energetic, and single-minded, I could learn a tune from tab without listening as I went along. (I doubt that I ever learned a song I had *never* heard, but I could work from a relatively distant memory.) Nowadays, I can't make sense out of tablature without careful, measure-by-measure listening. Must be old-timer's disease.