2015 file extension - Any data file created in 2015
What is 2015 file? How to open 2015 files?
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).