Files with .yesterday file extension can be most often encountered as various data or backup files. Can be pretty much anything, most notably tax and accounting data, calendar or backup files.
YESTERDAY file extension - Any data file created yesterday
What is yesterday file? How to open yesterday files?
File type specification:
The yesterday file extension might be used for any data file created previous day, typically as some kind of backup to distinguish the data from previous years.
Such files are most frequently used by various tax preparation software, but might as well contain calendar, business or just be backup of some sort.
