Re: [TUHS] First ARPAnet transmission

[John Labovitz <johnl@johnlabovitz.com>]

On Oct 29, 2018, at 10:19 AM, Clem Cole <clemc@ccc.com> wrote:

> 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	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

I wouldn’t say that’s definitive, but usually tzdata is a pretty good source.

Best,
—John