time-stamp-warn-inactive

time-stamp-warn-inactive is a variable defined in `time-stamp.el'.
Its value is

t

Documentation:
Have M-x time-stamp warn if a buffer did not get time-stamped.
If non-nil, a warning is displayed if `time-stamp-active' has
deactivated time stamping and the buffer contains a template that
otherwise would have been updated.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 19.29 of Emacs.