Hello again TheLearner, the Lord Jesus, because He is God, has always had a Divine nature, and He always will, but He took on a second nature, a human nature, at His Incarnation (and He is now BOTH fully God AND fully man, such that He now has a dual nature that was, is and will continue to be unique to Him alone, forevermore).
That said, we are told that He chose to set aside some of His Divine attributes (like Omniscience) when He lived among us as a man .. e.g. Philippians 2:5-8 cf Matthew 24:36. How AND why He chose to do so is a Biblical mystery, answerable by us, for now anyway, only by conjecture.
So, while the Lord Jesus Christ has always been/will always be fully God, with the same full array of Divine attributes that He (along with His Father and the Holy Spirit) has always had/will always have, there was a brief time in history when He chose not to access all of them (I believe that He did so because it was necessary for Him to do so, for our sakes, but even this is speculative).
God bless you!!
~Deuteronomy (David)
p.s. - the Amplified Bible seems helpful. See below.
Philippians 2 (Amplified Bible)
5 Have this same attitude in yourselves which was in Christ Jesus [look to Him as your example in selfless humility],
6 who, although He existed in the form and unchanging essence of God [as One with Him, possessing the fullness of all the divine attributes—the entire nature of deity], did not regard equality with God a thing to be grasped or asserted [as if He did not already possess it, or was afraid of losing it];
7 but emptied Himself [without renouncing or diminishing His deity, but only temporarily giving up the outward expression of divine equality and His rightful dignity] by assuming the form of a bond-servant, and being made in the likeness of men [He became completely human but was without sin, being fully God and fully man].
8 After He was found in [terms of His] outward appearance as a man [for a divinely-appointed time], He humbled Himself [still further] by becoming obedient [to the Father] to the point of death, even death on a cross.
Matthew 24 (Amplified Bible)
36 Of that [exact] day and hour no one knows, not even the angels of heaven, nor the Son [in His humanity], but the Father alone.