On what day did the apostles receive the Holy Spirit?

On the day of the Pentecost in the upper room.

Acts 2New King James Version (NKJV) Acts 2

Coming of the Holy Spirit

1 When the Day of Pentecost had fully come, they were all with one accord[a] in one place. 2 And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. 3 Then there appeared to them divided tongues, as of fire, and one sat upon each of them. 4 And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance.

The 1st Pentecost fell on a Sunday and was 50 days (meaning of Word) from the day of Jesus' Resurrection (Saturday - 7x7=49 plus 1 day).