On Monday, 29 October 2018 at 11:34:50 -0400, John Labovitz wrote:
> On Oct 29, 2018, at 10:19 AM, Clem Cole <clemc@ccc.com> wrote:

Ah, damn, you got there first.  Thanks for the zdump reference.

>> I >>think<< it is more likely 06:30 UTC, as IIRC Daylight Saving
>> Time finished mid-month so I think it would have been UTC+8:00 [not
>> +7:00 which it would be now].  That said, Nixon [...shutter...] was
>> in office and he put the US went on DST in the winter at some point
>> due to the oil crisis (but I thought that was a year or so later).
>> I remember it all happening at the time - but I can do not put
>> precise dates on any of it.
>
> According to tzdata...
>
> $ zdump -v America/Los_Angeles | grep 1969
> America/Los_Angeles  Sun Apr 27 09:59:59 1969 UTC = Sun Apr 27 01:59:59 1969 PST isdst=0
> America/Los_Angeles  Sun Apr 27 10:00:00 1969 UTC = Sun Apr 27 03:00:00 1969 PDT isdst=1
> America/Los_Angeles  Sun Oct 26 08:59:59 1969 UTC = Sun Oct 26 01:59:59 1969 PDT isdst=1
> America/Los_Angeles  Sun Oct 26 09:00:00 1969 UTC = Sun Oct 26 01:00:00 1969 PST isdst=0
>
> ...it appears that DST was *not* in effect on October 30, 1969.
>
>> A caveat: tzdata???s docs warn that dates before 1970 may not be
>> accurate. But because I???m fascinated by the cultural history
>> embedded within that database, I downloaded the latest tzdata files
>> to check. The relevant rules are in the ???northamerica??? file:
>
# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER
> Rule	CA	1948	only	-	Mar	14	2:01	1:00	D
> Rule	CA	1949	only	-	Jan	 1	2:00	0	S
> Rule	CA	1950	1966	-	Apr	lastSun	1:00	1:00	D
> Rule	CA	1950	1961	-	Sep	lastSun	2:00	0	S
> Rule	CA	1962	1966	-	Oct	lastSun	2:00	0	S
> Zone America/Los_Angeles -7:52:58 -	LMT	1883 Nov 18 12:07:02
> 			-8:00	US	P%sT	1946
> 			-8:00	CA	P%sT	1967
> 			-8:00	US	P%sT

Yes, but the key here is the US in the last line.  That refers to the
rules further up (US) that I referred to.

Greg
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