Is it possible to restore a 3rd party app from Time Machine?

It's not the program that you want from the day before, but whatever document you were editing and where you made a mistake.

How to do that depends on the program in question.

You could restore the file by opening the Time Machine interface, or maybe the program allows you to revert the document to a previous version from the program itself.

The program stays the same, it's the document itself that changes as you work with it. So you want to find an earlier version of the document. Open Time Machine go to the folder location of the file with which you were working. Dial back the time and then restore that version of the file to a safe location on your computer before opening it. Do this now since unless you had a backup drive attached to your computer today, Time Machine may only store a day's worth of changes on the computer itself.

Note that some programs (incidentally called "applications"—for us old-timers— or "apps" on a Mac) let you "undo" recent changes. That's usually under the Edit header in the application. This only tends to be the last couple of changes (repeat the "undo" function until it stops changing things) which may mean undoing the last few words you wrote. I wouldn't hold out much there unless it was something you did just before finishing yesterday.

MemaDeb wrote:

While working in my accounting program yesterday, the program made a bunch of changes resulting in negative balances that shouldn't be there. Is it possible to open the program from the day before through time machine? I don't want to restore my whole desktop, just this one application. I have found the application in time machine but not sure how to proceed from here.

The application should be in Time Machine. However, it would require a complete wipe and reinstall of the entire computer. Individual documents can be restored from Time Machine, but that's only possible if you know which document you want to restore. The internal database of an accounting tool probably consists of many different files, deep inside some hidden directory. The best you could do is corrupt the data.

Personally, I would think that a good accounting tool would allow you to go back in time and see the balance on any given date, and changes. But I don't know if any such good accounting tool exists. The ones that I've tried I immediately deleted.

You would have to find out from the developer where and how the data file is stored. You might then be able to restore a file that was made previous to the problem.

The data could be stored in such a way that it’s not possible to restore an older file. The developer should be able to tell you whether that’s possible and how to go about doing it.