Acts 12:4 has “Easter” in the AV. All other versions have “Passover.” Which is correct?
Easter is the correct translation, because Passover had already happened. Notice verse 3 says “(Then were the days of unleavened bread.)”. Verse 4 says “intending after Easter to bring him forth to the people.”
Herod put Peter in prison to hold him until after Easter, which hadn’t happened yet. But this was during the days of unleavened bread.
Notice Numbers 28:16-17 says, “And in the fourteenth day of the first month is the passover of the Lord. And in the fifteenth day of this month is the feast: seven days shall unleavened bread be eaten.” The seven feast days, the days of unleavened bread, come after the Passover. See also 2 Chronicles 30:15 & 21, Ezra 6:19 & 22.
The Passover happens on the 14th day of the month, and the days of unleavened bread are from the 14th to the 21st days. Therefore, if Acts 12 takes place during the days of unleavened bread, then the Passover had already taken place. Herod celebrates Easter, not Passover. He plans to keep Peter in jail until after Easter, when at least some, if not all, of the days of unleavened bread had already transpired, which means the Passover had already taken place. Thus Easter is the correct translation.