Season 4 CW moves Supergirl to Sunday

I really don't know what to make of this.
Does the CW believe Supergirl is a strong enough show to anchor it's new Sunday line up?
Or do they believe the built in fan base for a new Charmed will tune in early for Supergirl?

That move is going to make my night!

On a major network (CBS, ABC, NBC) that would be the time slot of death. Usually shows that are in trouble get put there. A good example is the last couple of seasons of Alias. Started out strong on a Friday or Saturday, but once ratings started to decline in later seasons so the show got dumped to Sundays. I think it survived for another season or two but that was it.

I am not sure what it means for CW. Saturday and Sunday were high profile slots back when Fox and UPN were trying to compete with the major networks. That was where shows like X-Files, Star Trek TNG, and Married with Children went. If that is the case, then it is a pretty strong show of confidence for Supergirl while moving Arrow to Mondays could be a signal that that show is in serious ratings trouble. However, I am not sure how any of this still holds true in today's TV market. Like many people, I am a cord-cutter so I get my shows via Internet streaming services.