The `Formatter` section of the `logging` module at https://docs.python.org/2/library/logging.html#formatter-objects reads like it's sufficient to create an instance of `Formatter` with default arguments (and set it as formatter of the `Handler` of a `Logger`) to have add timestamps to logging output.

Not to my eyes.  It clearly says that if no formatting string is specified, the default is used, and that formatTime is used only if the message string contains asctime.  Up to Vinay whether he thinks it is worth adding something like "which does not include a reference to the date/time" after the mention of using the default message if fmt is not supplied.

Perhaps I'll just change it to say 

... the default value of '%(message)s' is used, which just includes the message in the logging call. To have additional items of information in the formatted output (such as a timestamp), see other placeholder variables ...

and then link to the "LogRecord Attributes" section.

Sounds good to me.

New changeset 5ce760e2cc59 by Vinay Sajip in branch '2.7':
Issue #24060: Made logging.Formatter documentation a little clearer.
https://hg.python.org/cpython/rev/5ce760e2cc59

New changeset 88c141233d1e by Vinay Sajip in branch '3.4':
Issue #24060: Made logging.Formatter documentation a little clearer.
https://hg.python.org/cpython/rev/88c141233d1e

New changeset 1c72e9c1b3b4 by Vinay Sajip in branch 'default':
Closes #24060: Merged documentation update from 3.4.
https://hg.python.org/cpython/rev/1c72e9c1b3b4