I don't know if this has already been discussed but what about if the intelligence isn't T's boon? He wanted to get the ability to save people and stop what was coming, so I would think that the day of deduction, by itself, is the boon he received. So likely he got access to extreme intelligence and some small part of Cultivation's future telling or he became a shard for some small period of time. Either way in this case it would explain why this day falls outside of the normal distribution of his intelligence.