It's blog-worthy for a "number" of reasons. We were given an ordinal number, seventh, when we needed its cardinal counterpart, seven. A cardinal number shows quantity; an ordinal number shows rank or position. Let's try using both in a sentence.
The earth and the heavens were created in seven days,
and God rested on the seventh day.
I will not rest in my pursuit of misspellings, fact errors and other typos. I'll sail the seven seas in search of them, if that's what it takes.