DOT issues final ruling on Indiana time zones

Jesper Norgaard Welen jnorgard at
Fri Jan 20 05:05:02 UTC 2006

I think your last interpretation finally got it right, this is what
the DOT says. But I think they goofed up something when they wrote the
DOT. The effect is that Indiana goes from GMT-5 to GMT-6 during one
and then to GMT-5 again one hour later??!

In reality, I'm sure what they wanted to do is to keep Indiana on GMT-5
and on Eastern time until Central timezone shifts to Daylight Saving,
then define that point in time to be the shift in timezone. Then nobody
in Indiana has to change wall clock in spring, until autumn when
CDT shifts back to CST. I'll bet you no matter what official documents
been issued they won't shift the wall clock one hour behind just to
it one hour ahead, an hour later.

In effect at 2:59:59 EST they will shift to 3:00:00 CDT without any wall
clock change. So the DOT text should have read
"The effective *time* of this rule is 2:00 a.m. CST Sunday, April 2,
which is the changeover *time* from Central Standard Time to Central
Daylight Saving Time"
... or they could have used "3:00 a.m. EST" to the same effect.

The rule should in tz-database format would then be
			-5:00	-	EST	2006 Apr 2 3:00
			-6:00	US	C%sT
In short, Indiana is on Eastern time until 3:00, and from then they are
Central (Daylight) time.

By the way I don't think the time 2:00:00 CDT exists for that date (from
earlier mail), even for any place in the world - but that is maybe more
a philosophical problem. 2:00:00 CST and 3:00:00 CDT would exist (at
the latter) because they are in fact, the same.

Jesper Nørgaard Welen

-----Original Message-----
From: Deborah Goldsmith [mailto:goldsmit at] 
Sent: Thursday, January 19, 2006 16:33
To: tz at
Subject: Re: DOT issues final ruling on Indiana time zones

Sorry for the spam; I swear this is the last message. If I still have  
it wrong, I'll let someone else straighten it out. :-)

In America/Indiana/Knox, on April 2, 2006:

1:59:59 EST is followed by 1:00:00 CST (because this location  
switches to Central Time at that moment, and it's Standard Time in  
that zone)
1:59:59 CST is followed by 3:00:00 CDT (the normal DST transition)

It doesn't happen in one step; if it went from 1:59:59 to 3:00:00, it  
would be on EDT, not CDT. If it went from 1:59:59 to 2:00:00, then  
Knox would be on CDT an hour before the rest of its time zone. Now,  
that actually makes sense (clocks wouldn't have to change), but it's  
not what the DOT ruling says. It says "Starke county moves from ET to  
CT at the moment of the DST transition in the ET zone."

Deborah Goldsmith
Internationalization, Unicode liaison
Apple Computer, Inc.
goldsmit at

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