In the Beginning and The End

I am rewatching Supernatural Season Five for the first time since I first saw it, some six years ago now. I've watched individual episodes since then, but never sat down to watch the whole season.

And I noticed something I have somehow missed for years.

In early season four. Dean goes back in time in an episode called In the Beginning. In early season five, he goes forward in time in an episode called The End. I never noticed the pattern of those episode names.