find 'yesterdays files'

[snippsat]

One more question if I may, the capital "Path", what is it?

Also look at.
Python 3's pathlib Module: Taming the File System

Since Python 3.4, pathlib has been available in the standard library.
With pathlib, file paths can be represented by proper Path objects instead of plain strings as before.
These objects make code dealing with file paths:

• Easier to read, especially because / is used to join paths together
  
• More powerful, with most necessary methods and properties available directly on the object
  
• More consistent across operating systems, as peculiarities of the different systems are hidden by the Path object
  

In this tutorial, you have seen how to create Path objects, read and write files,
manipulate paths and the underlying file system, as well as some examples of how to iterate over many file paths.