Here's where I made my mistake.
1. the checkmark in the tools menu selects icons for the graphic menu.
2. I hadn't previously realized the labels in the tools menu have an action of their own:
a. nothing
b. toggle
c. submenu
d. direct action -- .e.g. close all tiddlers.
3. i also didn't realize it's not necessary to select the checkmark next to the label, so i unnecessarily moved the "timestamps are on" to the graphic menu. where it showed up between the "tag manager" and the "save changes" icons, so
4. at some point, in my ever hasty mouse chase, dragged the little rascal thru the icon and toggled the "timestamps" to the OFF state.
Thanks Jeremy, I hope this is of help to others.