There is only one place where the KJV uses the word "Easter" and most every student of the scripture knows the place:
Acts 12:1-4 KJV
1 Now about that time Herod the king stretched forth his hands to vex certain of the church.
2 And he killed James the brother of John with the sword.
3 And because he saw it pleased the Jews, he proceeded further to take Peter also. (Then were the days of unleavened bread.)
4 And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter to bring him forth to the people.
It is not "Easter" but the Pascha, (το πασχα), which is most everywhere else rendered "the Passover". Moreover it is not "after Easter" but rather "
WITH-AMIDST the Passover" in the above, (μετα το πασχα, "with-amidst the Passover"), but in this sense it means "with the end" or "at the end", yet still within the time frame given by the context because meta means with-amidst-within: and the time frame context is clearly "the days of Unleavened Bread", which were already in progress, during which Peter was taken and imprisoned by Herod, (and "the Passover" is mentioned secondarily because this Passover is clearly at the end of Unleavened Bread).
This passage therefore concerns the same day and the same custom as in the OP passages in the following thread where this has been explained,
Atzeret-Exodion, (the seventh and final day of Passover Unleavened Bread). And since there are two days singled out apart from the whole "feast of Unleavened Bread" in the Torah, which two days are also called "feasts", (for the seventh day is also called a feast in Exodus 13:6), it is shown herein that both the first and the seventh days were called the Passover. Eventually the whole week became known as Passover and-or Unleavened Bread and the two terms became more or less interchangeable as they are today. But in the context above the author plainly states that it was already the days of Unleavened Bread when Peter was thrown into prison. Herod therefore had intended to bring Peter forth to the people at the same time of the custom we read about in the Gospel accounts, where Bar-Abbas was released in the custom of the release, (Atzeret-Exodion), which was the last day, the seventh day, the final "feast day" of Passover Unleavened Bread. If therefore one reads the author as calling the seventh day, "the Passover", then "with" or "amidst", (μετα), makes perfect sense all by itself because the final Passover had not yet occurred when Herod cast Peter into prison, (for it was yet during the days of Unleavened Bread). In other words the author is calling the seventh day of Unleavened Bread, "the Passover", meaning that both the first day and the last day were called, "the Passover", (as well as the whole feast).
Acts 12:3-4
3 And when he saw that it pleased the Yhudim, he proceeded to seize Peter also: and these were the days of Unleavened Bread.
4 And when he had taken him, he put him in prison and delivered him over to four quaternions of soldiers to guard him, intending with-amidst the Passover to bring him forth to the people.
You all therefore do terribly err because the final day of the feast is called the feast of Meshiah as even called by some Jews and celebrated as such to this day: and it is the day in which the Sea of Reeds is parted and the sons of Yisrael pass|over into the Sanctuary of the Father, (Exodus 15:11-19, (see specifically Exodus 15:16, 17)).