System preferences have already been replaced with new ones, it's automatic.
What "Finder window" were you looking in that shows Today, Yesterday, etc.?
To delete the system preferences you must have been inside your Library/Preferences folder, but that does not explain the Finder window
Can you use Time Machine to restore the missing file? You do have backup for your stuff, right?
What does not work any longer??
P
Hi, I by mistake deleted System preferences and blutooth file exchange applications. In the finder window, I was looking into Today, Yesterday (monitors all the actions done) and thought its just a log and deleted them, which in turn deleted the original application. I even emptied the trash. Please help me to get back those applications.

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