What holy day did God send his holy spirit on to birth the new testment?

Answer 1

it is unknown when exactly Jesus sent the Holy Spirit, but it was after he had ascended up into heaven, on the day of Pentecost. Here is a Bible passage explaining it:

Acts 2:1-36
The Holy Spirit Comes at Pentecost 1When the day of Pentecost came, they were all together in one place. 2Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. 3They saw what seemed to be tongues of fire that separated and came to rest on each of them. 4All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.
5Now there were staying in Jerusalem God-fearing Jews from every nation under heaven. 6When they heard this sound, a crowd came together in bewilderment, because each one heard them speaking in his own language. 7Utterly amazed, they asked: "Are not all these men who are speaking Galileans? 8Then how is it that each of us hears them in his own native language? 9Parthians, Medes and Elamites; residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, 10Phrygia and Pamphylia, Egypt and the parts of Libya near Cyrene; visitors from Rome 11 (both Jews and converts to Judaism); Cretans and Arabs - we hear them declaring the wonders of God in our own tongues!" 12Amazed and perplexed, they asked one another, "What does this mean?"
13Some, however, made fun of them and said, "They have had too much wine."
Peter Addresses the Crowd 14Then Peter stood up with the Eleven, raised his voice and addressed the crowd: "Fellow Jews and all of you who live in Jerusalem, let me explain this to you; listen carefully to what I say. 15These men are not drunk, as you suppose. It's only nine in the morning! 16No, this is what was spoken by the prophet Joel:
17" 'In the last days, God says,
I will pour out my Spirit on all people.
Your sons and daughters will prophesy,
your young men will see visions,
your old men will dream dreams.
18Even on my servants, both men and women,
I will pour out my Spirit in those days,
and they will prophesy.
19I will show wonders in the heaven above
and signs on the earth below,
blood and fire and billows of smoke.
20The sun will be turned to darkness
and the moon to blood
before the coming of the great and glorious day of the Lord.
21And everyone who calls
on the name of the Lord will be saved.'
22"Men of Israel, listen to this: Jesus of Nazareth was a man accredited by God to you by miracles, wonders and signs, which God did among you through him, as you yourselves know. 23This man was handed over to you by God's set purpose and foreknowledge; and you, with the help of wicked men, put him to death by nailing him to the cross. 24But God raised him from the dead, freeing him from the agony of death, because it was impossible for death to keep its hold on him. 25David said about him:
" 'I saw the Lord always before me.
Because he is at my right hand,
I will not be shaken.
26Therefore my heart is glad and my tongue rejoices;
my body also will live in hope,
27because you will not abandon me to the grave,
nor will you let your Holy One see decay.
28You have made known to me the paths of life;
you will fill me with joy in your presence.'
29"Brothers, I can tell you confidently that the patriarch David died and was buried, and his tomb is here to this day. 30But he was a prophet and knew that God had promised him on oath that he would place one of his descendants on his throne. 31Seeing what was ahead, he spoke of the resurrection of the Christ, that he was not abandoned to the grave, nor did his body see decay. 32God has raised this Jesus to life, and we are all witnesses of the fact. 33Exalted to the right hand of God, he has received from the Father the promised Holy Spirit and has poured out what you now see and hear. 34For David did not ascend to heaven, and yet he said,
" 'The Lord said to my Lord:
"Sit at my right hand
35until I make your enemies
a footstool for your feet." '

36"Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ."- Acts 2:1-36

Answer 2

The day of resurection. Jesus said I leave with you the Holy Spirit. dave The day when Jesus was baptized, as he came out of the water. dave