How can I generate a cumulative plot where I can view the number of files by the last modified date?

I have a large (millions) number of files in a folder, its subfolders and its subsubfolders that were modified over the past 15 years. I'd like to generate a cumulative plot where I can view the number of files by the last modified date, e.g: How can I generate a cumulative plot where I can view the number of files by the last modified date? If that matters, I use Ubuntu.