Time window
Time windows are prohibited within DarkNight Matrix. It is believed that all of us, wherever we are in this universe, exist within a time window set in the year 1976. This time window presumably contains 4 trillion identical universes. We switch universes approximately every 5,800 years and experience the exact same life as in the previous universe. Technologically possible, but not permitted.
In 1988, another time window is expected to open, containing another 4 trillion universes.