Thanks for the reminder!
Whether I sign or date has depended so much on how I feel about a drawing when I complete it, which is not necessarily the most clear-headed moment in the process. I find exploratory sketches that I didn't like enough to date, but in retrospect were clearly steps into better seeing/drawing -- only they contained beginner's finding-the-way mistakes one might expect, but those glitches frustrated me badly at the time. But when I look back through sketchbooks, I'm frustrated by the missing dates!
Gesture drawing have always suffered badly from this. Hopefully I can now get past that need to judge, and just date them all as a practical habit.
