Day & Zimmermann is a privately held company that provides construction and engineering services, staffing services, and defense services. The company was founded in 1901 and is headquartered in Philadelphia, Pennsylvania. Day & Zimmermann has operations in the United States, Canada, and Europe. The company's construction and engineering services include power plant construction, maintenance, and decommissioning, as well as industrial construction and maintenance. Day & Zimmermann's staffing services provide temporary and permanent staffing solutions for a variety of industries, including engineering, construction, and defense. The company's defense services include munitions manufacturing and maintenance, as well as security services.