NOTE: Test both clean install & upgrade.
# Part 1
# login to Admin Console
# go to {nav Website & Content > Structure & Data} section
# click on `Sections` tab in main frame
# open `Directory` category for editing
# change value in `Created On` to become invalid (e.g. replace one digit with a letter)
# press `Save` button
# confirm, that validation error looks like `Incorrect date format, please use (XXX) ex. (YYY)`, where `XXX` is field format and `YYY` is sample value in that format
# press `Cancel` to close popup/modal window
# Part 2
# login to Admin Console
# go to {nav Website & Content > Labels & Phrases} section
# in translation of `la_err_bad_date_format` phrase replace `{format}` and `{sample}` with '%s`
# repeat test in `Part 1`