And I will show wonders in the heavens and in the earth: Blood and fire and pillars of smoke.

The sun shall be turned into darkness, And the moon into blood, Before the coming of the great and awesome day of the Lord.

joël 2:30-31

Peter quotes this pasage in Acts 2 and connects it with the out-pouring of the Holy Spirit.
So one could argue that this is already fulfilled.

But as far as I know, these specific verses are not seen as fulfilled at pentacost then. Or at least are expected to have a further fulfillment.

We expect this because these signs are also in Revelation and elsewhere in the bible.

Multitudes, multitudes in the valley of decision!
For the day of the Lord is near in the valley of decision.

The sun and moon will grow dark, And the stars will diminish their brightness.
The Lord also will roar from Zion, And utter His voice from Jerusalem;
The heavens and earth will shake; But the Lord will be a shelter for His people, And the strength of the children of Israel.

joël 3:14-16

I looked when He opened the sixth seal, and behold, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became like blood.

And the stars of heaven fell to the earth, as a fig tree drops its late figs when it is shaken by a mighty wind.

Then the sky receded as a scroll when it is rolled up, and every mountain and island was moved out of its place.

And the kings of the earth, the great men, the rich men, the commanders, the mighty men, every slave and every free man, hid themselves in the caves and in the rocks of the mountains,

and said to the mountains and rocks, “Fall on us and hide us from the face of Him who sits on the throne and from the wrath of the Lamb!

For the great day of His wrath has come, and who is able to stand?”

Revelation 6:12-17