Was that Pentecost in the Acts also a time of the year of jubilee?

As much as the Jubilee is important in Scripture, there is no evidence that one was ever actually declared in Israel's history.

This is noted as such by Jeffrey Fager and D.P. O'Brien in unrelated papers.

As such, there is no base from which to calculate the 50th year. More to the point for this question, there is no archeological or historical evidence of such a proclamation in the first half of the 1st century. (None later either, but since we don't know for certain when the Resurrection happened ( estimates range from 30 to 33 to 36 AD), I would be willing to consider any such declaration.) Unfortunately, there is none to be found.

That said, Jesus himself assuredly was the Jubilee. He says as much in Luke 4, when he preached on Isaiah 61:

He went to Nazareth, where he had been brought up, and on the Sabbath day he went into the synagogue, as was his custom. He stood up to read, 17 and the scroll of the prophet Isaiah was handed to him. Unrolling it, he found the place where it is written:

“The Spirit of the Lord is on me, because he has anointed me to proclaim good news to the poor. He has sent me to proclaim freedom for the prisoners and recovery of sight for the blind, to set the oppressed free, 19 to proclaim the year of the Lord’s favor.”[f]

20 Then he rolled up the scroll, gave it back to the attendant and sat down. The eyes of everyone in the synagogue were fastened on him. 21 He began by saying to them, “Today this scripture is fulfilled in your hearing.”

The "Good News" is the Gospel that Jesus has redeemed his own. Man may have been lax in keeping the Jubilee, but God was faithful in declaring it nonetheless.

The Jubilee itself is heavily bound up wit the idea of redemption:

Corollary to this provision was the right of redemption (ge˒ullâh) attached to the sale of any land by a Hebrew. One did not have to wait for the Year of Jubilee to recover one’s land; rather, it could be reclaimed at any time by the gō˒ēl (redeemer), a kinsman of the original owner, or by the owner himself, upon payment of a sum proportionate to the number of harvests remaining from the time of re-purchase to the next Jubilee Year (Lev 25:24–28). In any case, the land was to revert to its original owner at the time of the Jubilee. The primary theological basis for the “release” of slaves, debts and land was Yahweh’s ownership of both the people and the land

In presenting himself as the "Redeemer," Jesus himself is setting up the analogy of God reclaiming his own - the reason behind the Jubilee. As such, we can state, Jesus is our Jubilee, because though we had been slaves to sin, God restored the rightful order.

Luke’s narration of Jesus’ sermon in Nazareth represents a particular development in the eschato logical use of Jubilee Year themes: Jesus himself is presented as the anointed (messianic) herald of the long-awaited Year of Jubilee.

The term “release” (aphesis) represents the primary theological and verbal connection with the levitical proclamation of Jubilee. The classical Greek employment of aphesis was in the legal sense of a “release” from office, marriage, obligation, debt or even punishment. The word was not used, however, in religious contexts. In the LXX, of the approximately fifty instances of aphesis, twenty-two are in Leviticus 25 and 27, where it translates in most cases the Hebrew yôḇel, “Year of Jubilee”; in other cases, most notably Leviticus 25:10, it translates derôr, “release.” Derôr, in fact, seems to have been the technical term of the prophets to indicate the Year of Jubilee, that is, “the year of release,” or “liberty,” as Jeremiah 34:8, 15, 17; Ezekiel 46:17; and Isaiah 61:1 indicate.

Green, J. B., McKnight, S., & Marshall, I. H. (1992). Dictionary of Jesus and the Gospels (396). Downers Grove, Ill.: InterVarsity Press.

In paying for our sin on the cross, Jesus pays the redemption price for the world he created. In calling us sons and slaves, "joint heirs with Christ," we are free. As such, the Jubilee is for us.