@steve-m's solution works for all user accounts due to writing a key to the "global domain" of "UserDefaults". If you would like to display seconds in date format for date properties of a file in the Finder app, then log in to your account and execute the following command in the Terminal app:

for current user:

    defaults write ~/Library/Preferences/com.apple.finder.plist AppleICUTimeFormatStrings -dict-add 1 "hh':'mm':'ss' 'a"

for all users: 

    defaults write -g AppleICUTimeFormatStrings -dict-add 1 "hh':'mm':'ss' 'a"

This solution uses the "application domain" preferences file of the Finder app instead of the "global domain, " which limits it to the Finder app of the current user only.

To find out other date formatting options, visit the following link: [nsdateformatter.com][1]


  [1]: https://nsdateformatter.com