Indiana Time

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Daylight Saving

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Eastern vs Central 
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Natural Time
One theory discussed by people who think about time zones is "natural time". This is the theory that noon local time should be at the same time as solar noon. Solar Noon itself drifts plus or minus 16 minutes during the year (see Solar Time for illustrations). For proponents of "natural time" the concept of solar noon being at 1pm or 2pm is practically an obscenity!

In The poor man's math blog Stefano Maggiolo provides the following chart. The red areas are areas where solar noon lags behind local time zone noon. The blue areas are where solar noon occurs before local time zone noon. The darker the color the more deviation from solar noon.

(Source: The poor man's math blog by Stefano Maggiolo.)

There is a lot of red on the map. This demonstrates that most of the world accepts solar noon being after time zone noon. The chart reflects standard time. During Daylight Saving Time the chart shifts to even more red where Daylight Saving Time is in effect.

A closer look at North America shows standard time zones in the United States. It is more common to have solar noon after local time zone noon. With Daylight Saving Time the blue disappears.

So what is "natural"? Most of the world has chosen to shift Solar Noon later in the day (following the preference of their citizens and interests of commerce). Solar noon itself is never a fixed time. There is no compelling reason why the sun must be at solar noon when the clock strikes noon.

Here is the USDOT's opinion from the 2006 ruling:
         The Department is mindful of the value and ease of setting time zones based on simple geography. Congress has recognized, however, that natural time and simple geography do not address the complexity of modern life. Accordingly, in addition to establishing time zones based simply on longitudinal lines, Congress adopted a standard for time zone decisions: "Regard for the convenience of commerce and the existing junction points and division points of common carriers engaged in interstate or foreign commerce." It is DOT's responsibility to consider requests for changes in time zone boundaries in light of the statutory standard, bearing in mind the need to address the effect on economic, cultural, social, and civic activities between neighboring counties in making decisions.