The U.S. state of Indiana is divided between Eastern and Central time zones. The official dividing line has generally moved progressively west from its original location on the Indiana– Ohio border, to a position dividing Indiana down the middle, and finally to its current location along much of the Indiana– Illinois border. In April 2006, several southwestern and northwestern counties reverted to Central time, although by late 2007 all but two had returned to Eastern time.
As Indiana is on the western frontier of the Eastern time zone, there was opposition from many in the state to observing daylight saving time for decades.  The 2005 decision by the Indiana General Assembly to implement daylight saving time state-wide beginning in April 2006 remains controversial.
Indiana observes Eastern Time, except for twelve of its 92 counties, which observe Central Time.  Six of these counties are in northwestern Indiana, near Chicago (which observes Central Time), and six are in southwestern Indiana, near Evansville, where the metro area includes portions of southeastern Illinois and western Kentucky, which also observe Central Time. The twelve counties are:
- Northwestern Indiana ( Chicago- Gary metropolitan area):
- Southwestern Indiana ( Evansville Metro Area):
Since April 2, 2006, all counties in Indiana observe daylight saving time.
The most extensive study of time zone history in Indiana has been published in The American Atlas (1978) by Thomas G. Shanks, where the author identifies 345 areas in the state with a different time zone history for each.
The tz database lists 11 time zones for Indiana, where each zone is defined as a geographic area that observed the same offsets from UTC since January 1, 1970 (the UNIX epoch). The diagrams in this article are colored to show these 11 zones and a key is provided below.
Before 1883 in the United States, most towns and cities set their own local time to noon when the sun was at its highest point in the sky. Since the sun reaches "high noon" four minutes later for every degree of longitude traveled towards the west, the time in every town was different. In Indiana, local mean time varied from GMT-5:39 in the east to GMT-5:52 in the west. With the emergence of the railroads, hundreds of miles could be traveled in a much shorter time, causing a train passenger to apparently experience several slight changes in time over the course of even a short rail trip. By 1883, the major railroads in the US agreed to coordinate their clocks and begin operating on "standard time" with four "time zones" established across the nation, centered roughly on the 75th, 90th, 105th, and 120th meridians west. On November 18, 1883, telegraph lines transmitted GMT to major cities, where each city was to adjust their official time to their proper zone.  The state capital in Indianapolis lies at approximately the 86th meridian (U.S. Census Bureau), closer to the center of the Central Time Zone at the 90th meridian than the center of the Eastern Time Zone at the 75th meridian.
Time zones were first adopted by the United States Congress with the Standard Time Act of 1918. All of Indiana was located in the Central Time Zone. It was at this time the dividing line between Eastern Time and Central Time was moved from the Pennsylvania-Ohio state line to the Indiana–Ohio state line. Daylight saving time (DST) was included in the original Standard Time Act. A year later, Congress repealed daylight saving time from the Standard Time Act of 1918, though some communities continued to follow it.  During World War II, daylight saving time was once again mandated by Congress to conserve energy. After the war, the mandate to observe daylight saving time was lifted again. 
In 1949, in a heated rural vs. city debate, the Indiana General Assembly passed a law to put all of Indiana on Central Standard Time and to outlaw daylight saving time. However, the law had no enforcement power, and it was largely ignored by communities who wanted to observe Eastern Standard Time.  The Indiana General Assembly passed a law to make Central Time the official time zone of the state in 1957, but permitted any community to switch to daylight saving time during the summer. The law did, however, make it illegal for communities to observe "fast time" (i.e., daylight saving time) during the winter months. Governor Harold W. Handley vowed to enforce the law by withdrawing state aid from communities who attempted to observe "fast time" during the winter, though legal obstacles forced the Governor to back down from his stance. Once again, the law was not enforceable, as individual communities continued to observe whichever time zone they preferred. 
In 1961, the Indiana legislature repealed the 1957 law making Central Time the official time of Indiana, which allowed any community to observe DST.  The Interstate Commerce Commission divided Indiana between the Central Time Zone and the Eastern Time Zone. Still, neither the time zone line nor daylight saving time were uniformly observed (see 50 FR 43745). The United States Congress later passed the Uniform Time Act of 1966 ( Pub.L. 89–387 April 13, 1966; 80 Stat. 107–108; 15 U.S.C. §§ 260– 267) to specify where and when daylight saving time was applied in the U.S., and authority was shifted to the United States Department of Transportation (USDOT). Prior to the passing of this law, each state was permitted to decide this issue for itself. Having the state split in two time zones was inconvenient, however, so Governor Roger D. Branigin petitioned the USDOT to place all of Indiana back in the Central Time Zone a year later.
Over the next two years, the USDOT conducted several hearings in response to Governor Branigan's petition. Citizens of northwest and southwest Indiana appeared to favor the Central Time Zone with observance of DST, while those from other areas of the state favored the Eastern Time Zone with no observance of DST. The USDOT chose 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 placed in the Central Time Zone with observance of DST. The remainder of the state was placed in the Eastern Time Zone; the state was given special dispensation to exempt parts of itself from DST. Most portions of the state that were in the Eastern Time Zone did not observe DST. However, Floyd, Clark, and Harrison counties, which are near Louisville, Kentucky; and Ohio and Dearborn counties, which are near Cincinnati, Ohio unofficially observed DST due to their proximity to those major cities that observed DST.
While the USDOT was considering where the time zone line should be, several broadcast companies filed a federal lawsuit in 1968 to compel the USDOT to enforce the observance of daylight saving time in Indiana, which they won. As a result, the USDOT was ordered to stop informing Indiana residents that the Uniform Time Act will not be enforced and to provide a plan for its enforcement (see Time Life Broadcast Company, Inc. v. Boyd, 289 F. Supp. 219 (S.D. Indiana 1968). ; Time Life being the then-owner of WFBM-TV (Channel 6) in Indianapolis).
In 1972, the Indiana General Assembly overrode a veto from Governor Whitcomb to place the Northwest and Southwest corners of Indiana in the Central Time Zone on daylight saving time, and to place the rest of the state on Eastern Standard Time, upon federal approval (see
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IC 1-1-8.1 ). Congress approved an amendment ( Pub.L. 92–267;86 Stat. 116) to the Uniform Time Act of 1966 to permit a state that lay in two time zones to exempt part of the state from daylight saving time, and President Richard Nixon signed it into law. 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 the Eastern Standard Time throughout the year. Several eastern Indiana counties (Ohio and Dearborn counties, near Cincinnati; and Floyd, Clark, and Harrison counties, near Louisville) chose to unofficially observe daylight saving time, despite the Indiana statute.
Pike County asked the USDOT to move it from the Central Time Zone to the Eastern Time Zone in 1977; the request was approved. Four years later, Starke County asked the USDOT to move it from the Central Time Zone to the Eastern Time Zone; in this case, however they did not find a sound reason for the move, and declined the request (see 46 FR 23500 and 46 FR 51786). But in 1985, the Indiana General Assembly, in Senate Concurrent Resolution 6 from 1985, asked the USDOT to move five counties in southwest Indiana ( Posey, Vanderburgh, Warrick, Spencer, and Gibson) from the Central Time Zone to the Eastern Time Zone. They denied the request, finding that the change would not serve the convenience of commerce (see 50 FR 25856, 50 FR 28959, and 50 FR 43745). By 1986–87, Jasper County, along with Starke County, which was making a time zone change request for the second time in four years, petitioned the USDOT to move them from the Central Time Zone to the Eastern Time Zone in 1987–89. They denied the petitions of both counties (see 51 FR 43644 and 52 FR 10119).
Attitudes began to change in the 1990s, as Indiana's convoluted time zone situation was seen as impeding the state's economic growth. Interstate travel and commerce were difficult as people wondered, "what time is it in Indiana?"  In 1991, Starke County petitioned the USDOT to move it from the Central Time Zone to the Eastern Time Zone for the third time. This time, the petition was granted, effective October 27, 1991 (see 56 FR 13609 and 56 FR 51997).
On April 29, 2005, with heavy backing from Governor Mitch Daniels' economic development plan, and after years of controversy, the Indiana General Assembly passed a law stating that, effective April 2, 2006, the entire state of Indiana would become the 48th state to observe daylight saving time. The bill was also accompanied by Senate Enrolled Act 127,  which required Governor Daniels to seek federal hearings from the USDOT on whether to keep Indiana on Eastern Time with New York City and Ohio or whether to move the entire state back to Central Time with Chicago. 
As a result of a review by the USDOT, eight counties were moved from the Eastern Time Zone to the Central Time Zone, effective April 2, 2006. These were Starke and Pulaski counties in the northwest and Daviess, Dubois, Knox, Martin, Perry, and Pike counties in the southwest.
The placement of Martin County into the Central Time Zone, while leaving adjoining Greene and Lawrence Counties in the Eastern Time Zone presented a particular problem for Naval Surface Warfare Center Crane, a large US Navy base that straddles all three counties. With the Eastern/Central dividing line running through the base, NSWC Crane was unable to fully comply with the realigned time zones. The base opted to recognize Central Time, since the portion in Martin County was larger than the portions in Greene and Lawrence combined. This decision presented a larger regional problem, for even though NSWC Crane is Martin County's largest employer, two-thirds of the base's employees live in Greene, Lawrence, Monroe, and other Eastern Time Zone counties. This meant that the vast majority of Crane's employees would live in one time zone but work in another. Furthermore, a business park under construction at Crane's west gate would also straddle the new dividing line, with businesses on one side of the street being in a different time zone from those on the other. After one year under this awkward arrangement, Martin County reconsidered their bid to be placed in the Central Time Zone and formally petitioned for a return to the Eastern Time Zone. 
Independent from the situation facing Martin County, Pulaski County also formally petitioned for a return to the Eastern Time Zone. Pulaski County Commissioners and County Council both voted unanimously on February 6, 2006, to declare home rule and stay on Eastern Time if a federal agency did not grant an appeal to change the time zone ruling. However, the county conceded on March 27, 2006, officially accepting Central Time and switching time zones on April 2, 2006.  After some residents pledged to unofficially continue observing Eastern Time, the county changed work hours for most county employees so that they were in sync with Eastern Time work hours.  Dubois, Daviess, Knox, and Pike counties also decided to ask the federal government to return them to the Eastern Time Zone, and Dubois did so on April 27, 2006.  The confusion involving the time status of these counties led to their being dubbed the "seesaw six." St. Joseph, Marshall, and Fulton counties overtly expressed interest in making another attempt to be changed to Central Time as of the end of 2006. 
On February 9, 2007, it was officially reported that the USDOT had approved Pulaski County's return to Eastern Time. The change went into effect on March 11, 2007, the date when daylight saving time resumed. 
On September 20, 2007, the USDOT approved a petition from the five southwestern counties (Daviess, Dubois, Knox, Martin, and Pike) to return to the Eastern Time Zone. The request was approved, effective when daylight saving time ended on November 3, 2007. A petition from Perry County to move to the Eastern Time Zone was denied. 
With the exception of Perry and Starke counties, all counties that were moved to the Central Time Zone in 2006 were moved back to the Eastern Time Zone in 2007.
The decades-long Indiana time zone debate remains controversial. Some argue that the entire state should move to Central Time, while some others would prefer to have the state return to the non-observance of DST.  
With a large agricultural heritage, many farmers oppose DST because their days are controlled by the sun, not the clock. Farmers are often dependent on younger workers whose parents want them home by dinner, and when the sun is up later in the evening, farmers miss out on recreational activities that only happen late. When the sun is still up at 9pm to 9:30pm, the farmer is still in the field, while others have been off work for hours. 
Opponents of putting the entire state on one time zone often cite out-of-state cities as their reason of opposition. For example, counties in Northwestern Indiana are part of the Chicago metropolitan area. Many residents commute to Chicago, which is on Central Time. Counties in the southeastern corner of the state are suburbs of cities such as Cincinnati, Ohio, and Louisville, Kentucky, who both observe Eastern Time. In the southwestern corner of the state, Evansville serves as the central hub of a tri-state area that includes southern Illinois and western Kentucky (both on Central Time).
Supporters of daylight saving time and a common time zone in Indiana often claim Indiana must adopt the time-keeping system of the Eastern United States to preserve interstate business with that region. Some believe that Indiana businesses have lost hours of productive time with out-of-state colleagues because the time quirks are too confusing to keep track of on a daily basis.  The confusion caused to outsiders featured prominently in the plot of an episode of The West Wing in which presidential aides unfamiliar with Indiana's non-observance of DST miss their return flight to Washington, D.C., on Air Force One and express consternation with the variances in the state's time measurement. 
Detractors of daylight saving time claim that scientific studies assessing the impact of the time policy change to DST in Indiana have identified a significant increase in energy usage and spending on electricity by Indiana households. Indiana households paid an additional $8.6 million in electricity bills according to University of California, Santa Barbara economics professor Matthew Kotchen and Ph.D. student Laura Grant,  while supporters of Daylight Saving Time point to studies such as Professor Kotchen, the Department of Transportation and organizations such as the California Energy Commission claim that the United States saves approximately 1% of energy when Daylight Saving Time is being observed. 
Another wrinkle in the issue is the unnatural geographic location of this Eastern-Time-Zoned region. In the western Indiana counties where Eastern time is observed (South Bend and Lafayette south to Terre Haute and Vincennes), around the summer solstice, the sun neither sets until after 9:20 pm, nor does it reach solar noon until almost 2:00 pm.  During the winter months when standard time is observed, school buses in western regions lose a valuable hour of the sun's rays as they pick up children in the morning. Another notable observation is that schools in the Eastern Time Zone of Indiana tend to have far more 2-hour delays, mainly due to the fact that sunlight is required for many road de-icing components to work.[ citation needed] With the sun rising as late as 8:20 am in some areas, available sunlight is inadequate to safely thaw the roads for school buses to pick up all their passengers on time.[ citation needed] The argument is that if the same area were in its geographically natural Central time zone, the sun would be up an hour sooner, and it would have an additional hour to thaw the roads every morning.  
One group that believes Indiana should be on Central Time with DST is the Central Time Coalition, formed in 2009. The group's stated reasons for restoring Central Time to Indiana includes the following claims:
- All of Indiana is geographically situated in the Central Time Zone, as defined by the line of longitude of 90 degrees west, with the natural eastern border of the time zone being 82 degrees 30 minutes longitude west, running east of Columbus, Ohio.
- There is a significant cost to education, in terms of lost hours of education due to one and two-hour school delays.
- Since Indiana's adoption of Eastern Time, there has been an increase in vehicle accidents.
- Indiana's teen suicide rate is higher than the national average.
|c.c.*||coordinates*||TZ*||comments*||UTC offset||DST||Location and counties within Indiana||Notes|
|US||+394606-0860929||America/Indiana/Indianapolis||Eastern Time - Indiana - most locations||−05:00||East of the 1961 divide: (all unlisted counties)
West of the 1961 divide:
|US||+410305-0863611||America/Indiana/Winamac||Eastern Time - Indiana - Pulaski County||−05:00||North West: Pulaski|
|US||+382931-0871643||America/Indiana/Petersburg||Eastern Time - Indiana - Pike County||−05:00||South West: Pike|
|US||+384038-0873143||America/Indiana/Vincennes||Eastern Time - Indiana - Daviess, Dubois, Knox & Martin Counties||−05:00||South West: Daviess, Dubois, Knox, Martin|
|US||+382232-0862041||America/Indiana/Marengo||Eastern Time - Indiana - Crawford County||−05:00||South West: Crawford|
|US||+381515-0854534||America/Kentucky/Louisville||Eastern Time - Kentucky - Louisville area||−05:00||South East: Clark, Floyd, Harrison||only part of the zone is in Indiana|
|US||+384452-0850402||America/Indiana/Vevay||Eastern Time - Indiana - Switzerland County||−05:00||South East: Switzerland|
|US||+404251-0740023||America/New_York||Eastern Time||−05:00||South East: Dearborn, Ohio||only part of the zone is in Indiana|
|US||+415100-0873900||America/Chicago||Central Time||−06:00||North West, near Chicago:
South West, near Evansville: Gibson, Posey, Spencer, Vanderburgh, and Warrick
|only part of the zone is in Indiana|
|US||+411745-0863730||America/Indiana/Knox||Central Time - Indiana - Starke County||−06:00||North West: Starke|
|US||+375711-0864541||America/Indiana/Tell_City||Central Time - Indiana - Perry County||−06:00||South West: Perry|
- Campbell, Alex (March 10, 2013). "Some Pine for Different Time in Indiana". The Indianapolis Star.
- http://www.in.gov/portal/files/TimeZones.pdf Retrieved 2011-01-01
- "A Brief History of Time (in Indiana)" (Press release). The Indianapolis Star. 2005-04-30. Archived from the original on 2012-09-25. Retrieved 2007-11-15.
- "What Time is it in Indiana?". Monroe County Community School Corporation. Archived from the original on 2006-11-18. Retrieved 2006-11-25.
- "Senate Bill 0127". State of Indiana. Retrieved 2006-11-25.
- "Martin County Rescinds Time Zone Change Decision". Inside Indiana Business. March 15, 2006. Archived from the original on February 29, 2012.
- Coyne, Tom (March 28, 2006). "Pressured, Pulaski shifts to Central". South Bend Tribune. Archived from the original on June 13, 2006. Retrieved 2006-11-25.
- Coyne, Tom (April 1, 2006). "Some counties resisting zone change". South Bend Tribune. Archived from the original on June 13, 2006. Retrieved 2006-11-25.
- "Dubois wants Eastern time". South Bend Tribune. April 28, 2006. Archived from the original on June 13, 2006. Retrieved 2006-11-25.
- Smith, Mike (April 22, 2006). "Time debate just keeps ticking on". South Bend Tribune. Retrieved 2006-11-25.[ permanent dead link]
- "49 CFR Part 71 [OST Docket No. 2006–26442] RIN 2105–AD65 Standard Time Zone Boundary in Pulaski County, IN" (Press release). United States Department of Transportation. February 9, 2007. Retrieved 2007-02-19.
- Corbin, Bryan (September 21, 2007). "Five Counties to Return to EST: Perry County petition is denied". Evansville Courier & Press. Retrieved 2006-10-25.
- Clewly, Robin (March 31, 2001). "What time is the noon meeting?". Wired.
- Davey, Monica (November 13, 2005). "A time-honored debate in Indiana: to spring forward, fall back or neither". The New York Times. Retrieved 2007-11-25.
- Maureen Groppe. "'President' to tackle Indiana time zone issue," Greater Lafayette Journal and Courier, September 15, 2002.
- Lahart, Justin (February 27, 2008). "Daylight saving wastes energy, study says". The Wall Street Journal. Retrieved 2008-04-01.
- Daylight Saving Time – Saving Time, Saving Energy Archived 2008-05-09 at the Wayback Machine
- Laboratory, US Department of Commerce, NOAA, Earth System Research. "NOAA ESRL Global Monitoring Division".
- Shatz, Amy (October 19, 2005). "Central, not eastern! Indiana sports guy tackles time zones; after Daylight Saving shift, Mr. Sagarin asks Hoosiers to keep sync with sun". The Wall Street Journal (Eastern Edition). New York, NY. Pg. A1.
- "Hoosiers for Central Time".
- Indiana Time Zone Map 13 KB PDF file is a graphical overview of what counties are on Central and Eastern Time Zones in the State of Indiana.