Justin Sullivan Getty Images A critical port workers’ union is shifting to a scheduled work stoppage on June 20 at the already crowded Auckland Harbor in California, just days before the union contract expires. The Auckland division of the International Longshore and Warehouse Union, or ILWU, announced that the work stoppage meeting would be shifted from night shift to day shift. According to a document received by CNBC, the first shift from 8 p.m. until 5 p.m. PT would be closed. Work will be resumed at the port at 6 p.m. A port official told CNBC that the change was made so that blacks could celebrate the Juneteenth holiday, which is Sunday, June 19, but will be widely observed on June 20. The shutdown is bad news for already broken supply chains. The day shift is much busier than the night shift, according to truck drivers familiar with the port. According to the CNBC Supply Chain Heat Map, Auckland Port is the port with the worst performance for moving container containers – an average of 9.5 days. Port officials were notified of the change in an email Friday morning. Zoom Icon Arrows pointing outwards ILWU did not immediately respond to a request for comment. The contract expires on July 1. The change in the time of this meeting has troubled the logistics experts. “Given the slowdown in the US economy, disruptions to export flows are never positive,” said Alan Baer, CEO of OL USA Shipping. “We need all sides of the supply chain to work, as this optimizes the short-term and long-term prospects for all involved.” The port of Auckland also saw a drop in exports and recently announced a partnership with the USDA to provide financial assistance to agricultural exporters.