All the standard (date and) time formats in langconfig only show the time to the nearest minute, which is fine and usable for almost all applications.

However, when investigating issues, (e.g. where you want to correlate Moodle logs, with other server logs, of trace exactly what a user was doing, it really helps to have the time including seconds.

The places I have in mind for ther are the logs and livelogs reports. and on the quiz review page, where the teacher sees the response history for each attempt. (It was this second thing - where I had to dive in the our database to get the timestamps, which made me realise that this needed to be done in the Moodle UI. Not evey Moodle user has a developer or DB admin on hand.)