This commitment was the result of legislation signed by President Richard Nixon in 1972, which placed most of Indiana in Eastern Time, except for the Northwest and Southwest counties, although they observed daylight saving and fall time. Debate in the city, the Indiana General Assembly passed a law to place all of Indiana on central standard time and ban daylight saving time. But in 1985, the Indiana General Assembly, in Senate Concurrent Resolution 6 of 1985, called on the USDOT to move five southwestern Indiana counties (Posey, Vanderburgh, Warrick, Spencer and Gibson) from the central time zone to the eastern time zone. Indiana enacted the statute, officially placing northwest and southwest Indiana in the central time zone, in observance of daylight saving time, and the rest of the state in Eastern Standard Time throughout the year.
Daylight saving time detractors say that scientific studies evaluating the impact of the shift in hourly policy to daylight saving time in Indiana have identified a significant increase in energy use and electricity spending by Indiana households. Supporters of daylight saving time and a common time zone in Indiana often assert that Indiana must adopt the Eastern United States timing system to preserve interstate business with that region. Several counties in eastern Indiana (Ohio and Dearborn Counties, near Cincinnati; and Floyd, Clark and Harrison Counties, near Louisville) chose to unofficially observe daylight saving time, despite Indiana law.