[tz] Beginner's help request

[Paul.Koning at dell.com]

> On Oct 18, 2017, at 8:58 AM, Daniel Ford <dfnojunk at gmail.com> wrote:
> 
> ...
> So I went looking for a place where these quadruple rules might apply.  My
> first search was for Baghdad, which turned up another issue in the current
> (2017b) Asia file that doesn't quite make sense to me.  From line 1146...
> 
> Rule	Iraq	1986	1990	-	Mar	lastSun	1:00s	1:00	D
> # IATA SSIM (1991/1996) says Apr 1 12:01am UTC; guess the ':01' is a typo.
> # Shanks & Pottenger say Iraq did not observe DST 1992/1997; ignore this.
> #
> Rule	Iraq	1991	2007	-	Apr	 1	3:00s	1:00	D
> Rule	Iraq	1991	2007	-	Oct	 1	3:00s	0	S
> # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
> Zone	Asia/Baghdad	2:57:40	-	LMT	1890
> 			2:57:36	-	BMT	1918     # Baghdad Mean
> Time?
> 			3:00	-	+03	1982 May
> 			3:00	Iraq	+03/+04
> 
> Because there is no *current* RULE for Baghdad (the last expired 2007
> according to the table), I assume that DST no longer occurs there.

I would not call that "no current rule".  The lines in the rule files specify offsets, and the time when that offset goes into effect.  For any given time, the offset that applies is the one specified by the most recent prior effective-time.  Your conclusion looks correct to me: since the most recent time change established standard time (on 10/1/2007) has not applied since then.

	paul