There are certain trading events that happen every quarter. As traders, it is our job to understand what these events are, how they impact the market, and how us traders (especially us shorter-term traders) need to change our game plan, mindset, and execution based on these events. We’ll review some important concepts that will help give you a greater understanding of the market and give you an edge for the rest of your trading career.
https://www.cmegroup.com/trading/equity-index/rolldates.html