Sandbox means a developing world with as few rules as possible. Giving timesets to daily PvP is like a game saying "ok, you all have to sit down now and have tea" - see EVE or DAOC or ANY good MMO ever do that?
As to your second point, you are right, it doesn't, but sandbox means open game environment with as few rules as posible. Again, apples and melons, and I would point you to Minecraft if you prefer. If I were a jackass I'd also say "move along"; but I won't.