Jesus can be God without knowing the day nor the hour because Jesus can choose not to exercise his attribute of omniscience. Omniscience is the capacity to know everything (source).
Omniscience is an ability, not a tenseless property of deity. Omniscience is the ability to know any fact correctly if one so wishes. God may choose for instance to not listen to the prayers of sinners, or to choose what areas He wishes to exercise His ability to foreknow (Jimi Bryan, 2021).
The lack of knowledge in Mark 13:32 and the growing in wisdom in Luke 2:52 is because all knowledge and all wisdom is hidden in the Lord Jesus Christ (Colossians 2:3). Why was it hidden? Because it is like a treasure that needs to be searched out. For the Lord Jesus, this searching of knowledge and wisdom was a natural part of his incarnation. The incarnation is the Lord Jesus Christ limiting himself by his own choice of becoming human in order to serve (He "emptied himself", by taking the form of one who serves, by being born in the likeness of humans, Philippians 2:7). It is during his earthly life that he grew in wisdom and was taught of knowledge by God the Father, which Jesus used to serve us: "I do nothing on my own but say only what the Father taught me" (John 8:28). "I came not to be served, but to serve" (Mark 10:45).
Jesus is himself is the only one who will judge on that day and hour (John 5:22). It is quite strange that the Lord Jesus did not know the day nor the hour of his very own day ("the day of the Lord" is a phrase used equally to both the Father and the Son in the Bible).
