[LEAPSECS] UNIX timekeeping in 1985

[Poul-Henning Kamp]

We are restoring a CBM-900 prototype coomputer in datamuseum.dk.

The CBM-900 ran Mark-Williams "Coherent" UNIX clone.

Here are some quotes from the manuals, for enlightenment and amusement.

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    Changing the time zone

	If you are not in the Greenwich time zone, you should change
	the file "/etc/profile" to specify your time zone. [...]
	To use timezone, you must give the names of your standard
	and daylight-savins time zones, and the location of your
	time zone in minutes west of Greenwich, England.  For example
	the command

		TIMEZONE=EST:300:EDT

	tells the COHERENT system that your standard time zone is Eastern
	Standard Time (EDT), your daylight-savings time zone is Eastern
	Daylight Time (EDT), and that you are located 300 minutes west of
	Greenwich.

	Note that the term "minutes west" refers to minutes of time, not
	minutes of longitude.  To calculate how many minutes of time your
	city is west of Greenwich, multiply its degrees of longitude by
	four; for example, Chicago is located 88 degrees west, which
	means that it is 352 minutes (5 hours and 52 minutes) west of
	Greenwich "in time".  If you are unsure of the longitude of your
	city, check any atlas.

------------

    date -- Print the date

	The COHERENT system keeps track of the time and date [...]
	Internally, the date and time is kept in seconds since January 1,
	1970 at 00:00:00 GMT.  This means that files created in one time
	zone and referenced in another time zone, will bear the correct
	time.  The time and date printed out is converted from the internal
	form to local time.

------------

    [discussion of TIMEZONE variable]


	For example, possible TIMEZONE settings for Central Standard Time
	are:

		TIMEZONE=CST:360
		TIMEZONE=CST:360:CDT
		TIMEZONE=CST:360:CDT:-1.1.4:-1.1.10
		TIMEZONE=CST:360:CDT:-1.1.4:-1.1.10:2:60

	The first setting provides conversions to standard time only, a
	convention used by many farmers.  The last three settings provide
	conversions to daylight time and specify the default conversion
	rules in increasing detail.

------------

	[...] stime sets the system time. [...] which contains the number
	of seconds since midnght GMT on January 1, 1970.

------------


-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
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Never attribute to malice what can adequately be explained by incompetence.