Putting the year first makes archiving easier. Your computer literally puts everything in order that way. Day first, and it will be sorted by the most frequently changing element.
Also year first allows you to timestamp your files, so they are sorted by what time you created them that day.
Sorting by day, at the end of the year you’ll have files from the first day of each month grouped together, then the second day, and so on. Still searchable, but not as orderly.