Not clear if He knew in His time on earth, but Jesus knows now for sure, ...
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He said he didn’t know while he was here on earth. I trust him.
It may be that there were certain things he gave up to become a man here on this earth to save us. This may have been one of them.
Jesus lived the full experience here as a human. He was tempted like us but yet still lived a sin free life. To live the full experience of a human, he willingly left his place with the Father to become a man.