Commentaries:
The phrase "Days of Unleavened Bread" is only used in two places (Acts 12:3; 20:6), and in these instances, Luke refers to a span of time that can be slightly longer than the seven days of the Feast. Aside from this, the seven-day observance itself is consistently called the "Feast of Unleavened Bread," showing that this is a time to celebrate.
David C. Grabbe
Why Do We Observe Unleavened Bread? (Part One)
Other Forerunner Commentary entries containing Acts 12:3:
Exodus 12:17
Amos 8:11-14
John 17:14
Acts 12:3