Upcoming Indiana time zone moves

[Arthur David Olson]

My current sense: in the absence of clarification from the United States
Department of Transportation (DOT), the way to proceed with the upcoming
Indiana time zone moves is to handle them as direct transitions from Eastern
Standard Time to Central Daylight Time (without wall clock changes).

1.  This reflects what's happened historically in other places.
2.  This reflects what I'd expect to happen in reality in Indiana--
    folks in the affected areas will not change their clocks.
3.  This reflects presumed regulatory intent. Given the peculiar
    characteristics of the particular second DOT chose for the transition,
    and the overwhelmingly larger number of seconds in a year,
    I believe it highly likely that DOT's choice was made with
    the intent of allowing the transition to occur without clocks changing.
    Also, there's no mention in the DOT docket of the need for changing
    clocks twice.

I've attached changes to the "zic" manual page that document the
reprogramming done back in the year 1996 to do direct transitions;
the changes also provide information on how to get (very close to)
a one-hour retreat followed one hour later by a one-hour advance.

Since the affected regions will spend an hour in a nether-region between
CDT and EST, perhaps a special time zone abbreviation is needed. The only
letter between C and E is D: "Decidedly Odd Time" (DOT) :-)

				--ado

------- zic.8 -------
*** /tmp/geta8763	Tue Jan 24 12:03:21 2006
--- /tmp/getb8763	Tue Jan 24 12:03:21 2006
***************
*** 411,424 ****
  .q Rolling
  if the leap second time given by the other fields should be interpreted as
  local wall clock time.
! .SH NOTE
  For areas with more than two types of local time,
  you may need to use local standard time in the
  .B AT
  field of the earliest transition time's rule to ensure that
  the earliest transition time recorded in the compiled file is correct.
  .SH FILE
  /usr/local/etc/zoneinfo	standard directory used for created files
  .SH "SEE ALSO"
  newctime(3), tzfile(5), zdump(8)
! .\" @(#)zic.8	7.22
--- 411,444 ----
  .q Rolling
  if the leap second time given by the other fields should be interpreted as
  local wall clock time.
! .SH NOTES
  For areas with more than two types of local time,
  you may need to use local standard time in the
  .B AT
  field of the earliest transition time's rule to ensure that
  the earliest transition time recorded in the compiled file is correct.
+ .PP
+ If,
+ for a particular zone,
+ a clock advance caused by the start of daylight saving
+ coincides with and is equal to
+ a clock retreat caused by a change in UTC offset,
+ .IR zic
+ produces a single transition to daylight saving at the new UTC offset 
+ (without any change in wall clock time).
+ If you want two separate transitions
+ (for example,
+ a one-hour retreat from
+ U. S. Eastern Standard Time
+ to
+ U. S. Central Standard Time
+ followed one hour later by a one-hour advance to
+ U. S. Central Daylight Time),
+ you can artificially
+ (and slightly inaccurately)
+ specify the UTC offset change as occuring a single second too early.
  .SH FILE
  /usr/local/etc/zoneinfo	standard directory used for created files
  .SH "SEE ALSO"
  newctime(3), tzfile(5), zdump(8)
! .\" @(#)zic.8	7.23