“At that day ye shall know, that I am in my Father, and you in me, and I in you.”
1611 King James Version (KJV)
14:20 At that day - When ye see me after my resurrection; but more eminently at the day of pentecost.
Joh 14:20 At that day ye shall know. "That day" began on Pentecost. There was no more doubting after the Holy Spirit was sent. "That day" still comes to every soul that wholly surrenders to the will of Christ (Joh 7:17).