Vzic indicates missing tz rules

[Andy McDonald]

I've been using 'vzic' (http://dialspace.dial.pipex.com/prod/dialspace/town/pipexdsl/s/asbm26/vzic/)
to convert tz data to iCal. vzic 1.3 issues the following - hopefully self-explanatory warnings when
run against tz/2006p:

-----------------
andy at zanzibar:~/packages/vzic-1.3$ ./vzic --pure
WARNING: Couldn't find a LETTER_S to use in FORMAT: C%sT in Zone: Asia/Macau Leaving TZNAME empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: TM%sT in Zone: Asia/Ashgabat Leaving TZNAME empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: CE%sT in Zone: Europe/Warsaw Leaving TZNAME empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: WE%sT in Zone: Atlantic/Azores Leaving TZNAME empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: Y%sT in Zone: America/Nome Leaving TZNAME empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: M%sT in Zone: America/Inuvik Leaving TZNAME empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: P%sT in Zone: America/Whitehorse Leaving TZNAME
empty
WARNING: Couldn't find a LETTER_S to use in FORMAT: P%sT in Zone: America/Dawson Leaving TZNAME empty
andy at zanzibar:~/packages/vzic-1.3$
-----------------

(this is a slightly modified version of vzic - see below; the '--pure' option is not important).

Following through in tz for America/Inuvik, we see:
-----------------
# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
Rule	NT_YK	1918	only	-	Apr	14	2:00	1:00	D
Rule	NT_YK	1918	only	-	Oct	27	2:00	0	S
...

Zone America/Inuvik	-8:54:52 -	LMT	1884
			-8:00	NT_YK	P%sT	1979 Apr lastSun 2:00
			-7:00	NT_YK	M%sT	1980
			-7:00	Canada	M%sT
-----------------

Significantly, America/Inuvik is defined explicitly from the 1800's onwards, but the rule NT_YK is
defined only from 1918, hence this missing 'LETTER/S'. Similar issues affect America/Whitehorse and
America/Dawson. America/Nome uses the rule 'US' from 1943 to 1946, although the rule isn't defined
for most of that period. Spot-checking the other problem zones indicates similar problems.

I've exchanged a few e-mails with the developer of vzic; he pointed out that vzic works around most
of the above 'problem' zones (see line 899 of vzic_output.c, v1.3); I commented out the workaround
to derive the above output. With the workaround, vzic warns on Inuvik, Whitehorse and Dawson only.

Andy