Why does 2 Peter 1:19 read differently in the NWT than in other Bibles?

While the hearts of mankind in general were—and still are—in darkness, that need not be so with true Christians. It is as if they have a lamp shining in what otherwise would be dark, their hearts. Peter knew that by paying attention to the illuminating prophetic word of God, Christians would keep alert and enlightened to the dawn of a new day. That would be the time when the “daystar,” or “bright morning star,” would actually reign in Kingdom power.