Time difference, current local time and date of the world's time zones have been extensively studied in Indiana. In 1949, the Indiana General Assembly passed a law to put all of the state on Central Standard Time and ban Daylight Saving Time. However, this law had no enforcement power and communities that wanted to observe Eastern Standard Time largely ignored it. The Indiana General Assembly passed legislation in 1957 to make Central Time the state's official time zone, but allowed any community to switch to Daylight Saving Time during the summer.
Governor Handley pledged to enforce the law by withdrawing state aid to communities that tried to observe the winter fast, although legal obstacles forced him to reverse his stance. In 1961, the Indiana legislature repealed the 1957 law that made Central Time official Indiana time, allowing any community to observe Daylight Saving Time. The Interstate Trade Commission divided Indiana between the Central Time Zone and the Eastern Time Zone. Even so, neither the time zone line nor Daylight Saving Time were observed uniformly. The United States Congress subsequently passed the Uniform Time Act of 1966 (Pub.
L.), which authorized each state to decide this matter for itself. Governor Roger D. Branigin asked the USDOT to return all of Indiana to the Central Time Zone a year later. After several hearings, the USDOT decided to divide Indiana between the Central Time Zone and the Eastern Time Zone. Six counties near Chicago (Lake, Porter, LaPorte, Jasper, Newton and Starke) and six counties near Evansville (Posey, Vanderburgh, Warrick, Spencer, Gibson and Pike) were located in the Central Time Zone while respecting Daylight Saving Time.
The rest of the state was placed in the Eastern Time Zone; however, parts of it were exempted from Daylight Saving Time. Most parts of the state that were in the Eastern Time Zone did not observe Daylight Saving Time. However, Floyd, Clark and Harrison Counties near Louisville, Kentucky and Ohio and Dearborn Counties near Cincinnati, Ohio unofficially observed Daylight Saving Time due to their proximity to major cities that observed it. In 1968, several broadcasting companies filed a federal lawsuit to force USDOT to enforce Daylight Saving Time in Indiana which they won. As a result, USDOT was ordered to provide a plan for its implementation.
In 1972, Indiana General Assembly overturned a veto by Governor Whitcomb to place northwest and southwest corners of Indiana in Central Time Zone during Daylight Saving Time and placing rest of the state at Eastern Standard Time subject to federal approval. Attitudes began to change in 1990s when Indiana's intricate time zone situation was considered impeding its economic growth. Interstate travel and commerce were difficult as people wondered what time it is in Indiana. In 1991 Starke County requested USDOT to move it from Central Time Zone to Eastern Time Zone which was granted with effect from October 27th 1991. A request from Perry County to move to Eastern time zone was denied. The decades-old Indiana time zone debate remains controversial with some arguing that entire state should switch to Central time while others would prefer that state not observe Daylight Saving Time again.
Supporters of Daylight Saving Time and a common time zone in Indiana often assert that Indiana must adopt Eastern United States timing system to preserve interstate business with that region.