Rules that Don't Exist

Ken Pizzini tz_ at
Sun Nov 25 05:57:51 UTC 2007

On Sat, Nov 24, 2007 at 07:12:55AM -0600, Bill Seymour wrote:
> On 11/23/07, Ken Pizzini <tz_ at> wrote:
> > The important thing to remember is that the rules specify *transitions*.
> That's what I thought, too, until I realized that the SAVE and LETTER/S
> columns specify states, not transitions.  Consider for example:
>  Rule  US  1942 only  -  Feb   9  2:00     1:00  W # War
>  Rule  US  1945 only  -  Aug 14  23:00u 1:00   P # Peace
> The second of those is /not/ an instruction to set my clock ahead an hour.

Though UTC/GMT offset didn't change, that's still a transition.
The name of (and abbreviation for) the zone *did* transition at 23:00u
on 1945-08-14.

> But my real question was about the replacement text for "%s" in the Zone's
> FORMAT when there has been no "transition" to set the LETTER/S initially.

Ah, right.  This came up before.  The correct answer is as you state here:

>     When changing to a named Rule before the first one exists, move
>     forward in time to the first with a SAVE of 0 and use the LETTER/S
>     from that.

This shortcoming of the zic.8 documentation has come up before, but no
consensus about how to word a fix was acheived.  Perhaps your suggestion
above will have better luck, or at least inspire a more fruitful round
of wordsmithing this time...

		--Ken Pizzini

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