configure Jupyter date format in metadata display, e.g. last checkpoint date

Question

On top of my notebook I currently have “Last Checkpoint: 01/25/2022 (autosaved)” displayed. I would like this in a civilised readable different format. However I can’t find the option to change this.

The only mentions of date in the template config file (generated with jupyter notebook --generate-config) are:

## The date format used by logging formatters for %(asctime)s
#  Default: '%Y-%m-%d %H:%M:%S'
# c.Application.log_datefmt = '%Y-%m-%d %H:%M:%S'

## The date format used by logging formatters for %(asctime)s
#  See also: Application.log_datefmt
# c.JupyterApp.log_datefmt = '%Y-%m-%d %H:%M:%S'

## The date format used by logging formatters for %(asctime)s
#  See also: Application.log_datefmt
# c.NotebookApp.log_datefmt = '%Y-%m-%d %H:%M:%S'

All of those seem to refer to the logging and not to the displayed date. The config file contains no mention of locale or language. None of the environment variables I’ve tried have had any effect (including LANG, LC_ALL, LC_TIME, etc.), though they do affect python’s locale.getdefaultlocale().

This is the output of jupyter --version for what it’s worth:

jupyter  --version
Selected Jupyter core packages...
IPython          : 8.0.1
ipykernel        : 6.7.0
ipywidgets       : 7.6.5
jupyter_client   : 7.1.1
jupyter_core     : 4.9.1
jupyter_server   : not installed
jupyterlab       : not installed
nbclient         : 0.5.10
nbconvert        : 6.4.0
nbformat         : 5.1.3
notebook         : 6.4.6
qtconsole        : 5.2.2
traitlets        : 5.1.1