The image on this post has the file location
https://www.organicweb.com.au/wp-content/uploads/2010/10/wordpress-300x300.png. I however uploaded the image to my WordPress website in September 2016. Also, when uploading files I’ve selected the Organise my uploads into month- and year-based folders option by going to Settings then Media from my WordPress dashboard. So why has WordPress saved the image to the October 2010 directory when the image was uploaded in September 2016?
What occurs in WordPress is that the image is uploaded to the directory reflecting the date of the post and not when the image was uploaded. In my example above I uploaded the image when editing a post published in 2010 and therefore the image has been saved in the 2010 directory on the server.
Oddly enough this is actually a feature rather than a bug. WordPress is designed to save images to the directory date of the post rather than the dates of when the image was updated.