Matthias is chosen to replace Judas
Between the ascension and Pentecost, about 120 believers met in Jerusalem. Peter proposed that someone who had been with them from John's baptism to the ascension take Judas's place, and the lot fell on Matthias.
They drew lots for them, and the lot fell on Matthias; and he was counted with the eleven apostles.
Acts 1:26 (World English Bible)
The eleven apostles, the women, Mary the mother of Jesus, and his brothers devoted themselves to prayer together (Acts 1:14). Two men who met the requirement were put forward, Joseph called Barsabbas and Matthias, and after prayer they cast lots. Matthias is not mentioned again in Scripture.
Places
Dating notes
In the ten days between the ascension (14 May) and Pentecost (24 May), AD 33, in Ussher's reckoning; the exact day isn't given.