On March 20th I answered this question. On October 6th I edited it since I decided that even though the question has a simple answer, my response was perhaps a bit too short. By conventional Earth standards, October 6th falls more than 6 months after March 20th, and nobody else appears to have answered, edited the question, or edited my answer. Should I have earned the "Excavator" badge for this? Does this badge not apply to self-edits? Or perhaps did somebody answer the question and then delete that answer in the interim?
We don't want to encourage self-bumping of content in an attempt to get votes by bumping it on the front page for the sake of doing so...it's meant to be focused on improving old content that needs love. While this may be true for self-edits, it could also be used to exploit the badge and rep system at the same time, so we exclude that case.