XYZ Was Formed as a Calendar-Year S Corporation with Xavier

Short Answer

XYZ was formed as a calendar-year S corporation with Xavier, Yolinda, and Zach as equal shareholders. On September 15, 2016, XYZ's S election was terminated after Zach sold his XYZ shares (one-third of all shares) to his solely owned C Corporation Zach, Inc. Absent permission from the IRS, what is the earliest date XYZ may again elect to be taxed as an S corporation?