.2015 is Any data file created in 2015
Key Features: .2015 File Extension
What is an .2015 file?
The 2015 file extension is maybe associated with various data file types. File could be created or backed up in 2015.
Also may include some kind of financial, tax preparation, business, calendar, schedule, accounting data.
If the file name contains two extensions, try to rename the file to the original extension (delete the 2015 extension from the file name).