Easter is only mentioned once in only one common translation: the King James Version.
Now about that time Herod the king stretched forth his hands to vex certain of the church. And he killed James the brother of John with the sword. And because he saw it pleased the Jews, he proceeded further to take Peter also. (Then were the days of unleavened bread.) 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.
What about the hundreds of other English translations (including the New King James) and other non-English translations? Why are they all Easter-less?
Almost every English translation of the "New Testament" comes from Greek manuscripts. In order to get G-d's Word from the original Greek into modern English somebody has to translate the Greek words for us.
The Greek word in Acts 12:4 that the KJV translators interpret as "Easter" is πάσχα (pronounced PAHskah) and commonly transliterated pascha. This word is Strong's #3957 and it is used 29 times in 27 verses. In every other instance the word is used in Scripture, the KJV authors translate this word as Passover.
"Easter" was invented around 200 CE by a sect of believers that came to be known as the Catholic church. It is anachronistic to read Easter into the events of Acts 12.
In fact, the Bible never mentions any of the common trappings of Easter:
- The Easter bunny
- Easter eggs
- Easter baskets
- Chocolate (or any kind of candy)
- Green plastic grass
- Little yellow chicks
- Easter dresses/bonnets/suits