The White House press office determines full lid timing based on the president's confirmed public schedule, pool reports, and any last-minute announcements or events. For the May 18-23 window, following President Trump's return from overseas travel the prior weekend, the calendar shows a typical mix of executive time, closed-press meetings, and in-town pool calls that often conclude by mid-to-late afternoon. Weekday activities may extend later due to legislative or diplomatic updates, while the weekend days frequently see earlier lids once official duties wrap. Traders monitor sources such as Roll Call calendars for the first explicit full lid announcement, with resolution hinging on whether that call occurs at or before 6:30 PM ET on each individual date.