Chicago and Houston are in the same time zone. Both cities use Central Time (CST/CDT). When it's noon in Chicago, it's also noon in Houston.
Both cities observe daylight saving time, switching between CST (UTC-6) in winter and CDT (UTC-5) in summer.
Any time works! Since both cities are in the same time zone, scheduling calls is never a problem. Business hours are identical.
Chicago and Houston are America's third and fourth largest cities. United Airlines hubs both cities, with frequent direct flights taking about 2.5 hours.