Mark 13:32

Neither the Son] This is the true reading not only here, but in Matthew 24:36, where it has been altered in many MSS, probably as being a difficulty to faith. Rightly to understand it, we must remember that Jesus possessed two complete and perfect natures, the divine and the human. In His divine nature He knew all things whatsoever, but in His human nature He knew only such things as He willed to know. And since it was not expedient that we should know the day and the hour of the Last Judgment, He willed to be ignorant of it. This avowed ignorance implies no limitation of Christ's divine nature. Christ had no will but His Father's. When the Father willed to withhold from Him any of His designs, His will was to be ignorant.

The Arians taught that the Son was ignorant even in His divine nature, but Athanasius replied, 'But lovers of Christ recognise that the Word did not say, “I know not,” as being the Word, for He knew; but He thus indicated His humanity, showing that ignorance is part of human nature.'