*****
There was no sense of day and night inside the tower. Everything depended on the desires of the Cylix and Novius. Whenever they wished, it was day. Whenever they wanted, it was night.
As the Tower also ran in a different space, they could even manipulate the flow of time inside the tower, completely detaching it from the outside World. Despite all that, they just preferred to stick as close to the real timeline as possible since there was no benefit in doing anything extra.
It was just with the training of Gabriel that they manipulated the flow of time, albeit only to a small extent. Since they believed Gabriel was going to train here for a long time, they didn't want to keep him away from the real world for too long as things could change really fast in the real world.
They only tweaked the time inside the tower only a tiny bit to make sure that two days inside the tower were equal to one day outside the Tower.