First, quit OmniFocus if it is running.
Launch the Terminal application, which is found in the Utilities folder in your Applications folder.
Then, copy and paste the following group of lines from your web browser into the Terminal (you can do them all at once):
Code:
defaults write com.omnigroup.OmniFocus RelativeDateFormatterShowTime YES
defaults write com.omnigroup.OmniFocus RelativeDateFormatterDefaultWantsTruncatedTime YES
defaults write com.omnigroup.OmniFocus RelativeDateFormatterUseRelativeDayNames YES
defaults write com.omnigroup.OmniFocus RelativeDateFormatterDateFormatStyle medium
Press the return key after you paste them into the Terminal window. Now launch OmniFocus and see how you like the new settings.