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* [TUHS] Re: Happy birthday, Unix timestamp!
@ 2022-09-09 18:53 Norman Wilson
  0 siblings, 0 replies; 9+ messages in thread
From: Norman Wilson @ 2022-09-09 18:53 UTC (permalink / raw)
  To: tuhs

Andrew Hume:

  if i recall correctly, V1 of Unix had time measured in milliseconds.
  were folks that sure that this would change before wrap-around?

====

Not milliseconds (which were infinitesimally small to the
computers of 1969!) but clock ticks, 60 per second.

Initially such times were stored in a pair of 18-bit PDP-7
words, giving a lifetime of about 36 years, so not so bad.

The PDP-11's 16-bit words made that a 32-bit representation,
or about two and a quarter years before overflow.  Which
explains why the time base was updated a few times in early
days, then the representation changed to whole seconds, which
in 32 bits would last about as long as 36 bits of 60 Hz ticks.

The PDP-7 convention is documented only in the source code,
so far as I know.  The evolution of time on the PDP-11 can
be tracked in time(II) in old manuals; the whole-seconds
representation first appears in the Fourth Edition.

Norman Wilson
Toronto ON
Not that old a timer, but once looked into old time

^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-08 23:48 ` [TUHS] " Rob Pike
  2022-09-09  0:11   ` Dan Cross
  2022-09-09  4:24   ` Rob Pike
@ 2022-09-11  0:09   ` Dave Horsfall
  2 siblings, 0 replies; 9+ messages in thread
From: Dave Horsfall @ 2022-09-11  0:09 UTC (permalink / raw)
  To: The Eunuchs Hysterical Society

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On Fri, 9 Sep 2022, Rob Pike wrote:

> There was a delightful conference in Copenhagen celebrating that event, 
> and I was lucky enough to attend. The slides of my talk live 
> here: http://herpolhode.com/rob/ugly.pdf
> 
> I flew back the next day, September 10, 2011, and it was a beautiful 
> clear night with a stunning view of the city. We sat in the last row of 
> the plane, and had an unobstructed view of the trade towers as we landed 
> near midnight. We went home, fell asleep, and were woken by a phone call 
> about 9am.
 
Cripes...  I remember it well.

-- Dave

^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-09 12:06 Douglas McIlroy
@ 2022-09-09 17:16 ` Andrew Hume
  0 siblings, 0 replies; 9+ messages in thread
From: Andrew Hume @ 2022-09-09 17:16 UTC (permalink / raw)
  To: Douglas McIlroy; +Cc: TUHS main list

if i recall correctly, V1 of Unix had time measured in milliseconds.
were folks that sure that this would change before wrap-around?

> On Sep 9, 2022, at 5:06 AM, Douglas McIlroy <douglas.mcilroy@dartmouth.edu> wrote:
> 
>> Well, you can imagine what happened when the leading digit changed
>> from an ASCII "9" to an ASCII "1". Oops.
> 
> I first saw a time-overflow bug more than 60 years ago. Accounting
> went haywire in the Bell Labs' comp center on day 256 of the year,
> when the encoded output of a new time clock reached the sign bit.
> 
> Doug


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
@ 2022-09-09 12:06 Douglas McIlroy
  2022-09-09 17:16 ` Andrew Hume
  0 siblings, 1 reply; 9+ messages in thread
From: Douglas McIlroy @ 2022-09-09 12:06 UTC (permalink / raw)
  To: TUHS main list

> Well, you can imagine what happened when the leading digit changed
> from an ASCII "9" to an ASCII "1". Oops.

I first saw a time-overflow bug more than 60 years ago. Accounting
went haywire in the Bell Labs' comp center on day 256 of the year,
when the encoded output of a new time clock reached the sign bit.

Doug

^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-09  3:29 ` Seth Morabito
@ 2022-09-09  7:03   ` Michael Kjörling
  0 siblings, 0 replies; 9+ messages in thread
From: Michael Kjörling @ 2022-09-09  7:03 UTC (permalink / raw)
  To: tuhs

On 8 Sep 2022 20:29 -0700, from web@loomcom.com (Seth Morabito):
> Well, you can imagine what happened when the leading digit changed
> from an ASCII "9" to an ASCII "1". Oops.

Let me guess. Something very similar to what happened to Microsoft
Exchange servers when the first two digits in a 32-bit signed integer
representation of the current date and time (formatted as YYMMDDHHMM)
changed from "21" to "22" as the date became January 1, 2022.

For those who don't immediately realize why that's a snafu: what is
the value of (2^31)-1 when interpreted as a string representation of a
timestamp according to that format, and how does that relate to Jan 1
2022?

-- 
Michael Kjörling • https://michael.kjorling.se • michael@kjorling.se
 “Remember when, on the Internet, nobody cared that you were a dog?”


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-08 23:48 ` [TUHS] " Rob Pike
  2022-09-09  0:11   ` Dan Cross
@ 2022-09-09  4:24   ` Rob Pike
  2022-09-11  0:09   ` Dave Horsfall
  2 siblings, 0 replies; 9+ messages in thread
From: Rob Pike @ 2022-09-09  4:24 UTC (permalink / raw)
  To: Dave Horsfall; +Cc: The Eunuchs Hysterical Society

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Oops, 2001 of course, but you knew that from multiple contextual clues.

-rob


On Fri, Sep 9, 2022 at 9:48 AM Rob Pike <robpike@gmail.com> wrote:

> There was a delightful conference in Copenhagen celebrating that event,
> and I was lucky enough to attend. The slides of my talk live here:
> http://herpolhode.com/rob/ugly.pdf
>
> I flew back the next day, September 10, 2011, and it was a beautiful clear
> night with a stunning view of the city. We sat in the last row of the
> plane, and had an unobstructed view of the trade towers as we landed near
> midnight. We went home, fell asleep, and were woken by a phone call about
> 9am.
>
> -rob
>
>
> On Fri, Sep 9, 2022 at 8:29 AM Dave Horsfall <dave@horsfall.org> wrote:
>
>> https://www.timeanddate.com/on-this-day/september/9
>>
>> ``Unix time or Unix epoch, POSIX time or Unix timestamp, is a time system
>>   that measures the number of seconds since midnight UTC of January 1,
>> 1970,
>>   not counting leap seconds. At 01:46:40 UTC on September 9, 2001, Unix
>> time
>>   reached the billionth second timestamp.''
>>
>> Hard to believe that it was that long ago...
>>
>> -- Dave
>>
>

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-08 22:28 [TUHS] " Dave Horsfall
  2022-09-08 23:48 ` [TUHS] " Rob Pike
@ 2022-09-09  3:29 ` Seth Morabito
  2022-09-09  7:03   ` Michael Kjörling
  1 sibling, 1 reply; 9+ messages in thread
From: Seth Morabito @ 2022-09-09  3:29 UTC (permalink / raw)
  To: tuhs

On Thu, Sep 8, 2022, at 3:28 PM, Dave Horsfall wrote:
> https://www.timeanddate.com/on-this-day/september/9
>
> ``Unix time or Unix epoch, POSIX time or Unix timestamp, is a time system 
>   that measures the number of seconds since midnight UTC of January 1, 1970, 
>   not counting leap seconds. At 01:46:40 UTC on September 9, 2001, Unix time 
>   reached the billionth second timestamp.''

I remember this event vividly because at work we had an important system fail.

There was a database that was storing the time into a VARCHAR column. Unfortunately, we were sorting on that column and using the table as a queue so we could always be sure to pick up the most recent entries and act on them.

Well, you can imagine what happened when the leading digit changed from an ASCII "9" to an ASCII "1". Oops.

-Seth
-- 
  Seth Morabito
  Poulsbo, WA
  web@loomcom.com

^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-08 23:48 ` [TUHS] " Rob Pike
@ 2022-09-09  0:11   ` Dan Cross
  2022-09-09  4:24   ` Rob Pike
  2022-09-11  0:09   ` Dave Horsfall
  2 siblings, 0 replies; 9+ messages in thread
From: Dan Cross @ 2022-09-09  0:11 UTC (permalink / raw)
  To: Rob Pike; +Cc: The Eunuchs Hysterical Society

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On Thu, Sep 8, 2022, 7:50 PM Rob Pike <robpike@gmail.com> wrote:

> There was a delightful conference in Copenhagen celebrating that event,
> and I was lucky enough to attend. The slides of my talk live here:
> http://herpolhode.com/rob/ugly.pdf
>
> I flew back the next day, September 10, 2011, and it was a beautiful clear
> night with a stunning view of the city. We sat in the last row of the
> plane, and had an unobstructed view of the trade towers as we landed near
> midnight. We went home, fell asleep, and were woken by a phone call about
> 9am.
>

You probably flew approximately over me. I was working late that night in
downtown Manhattan, a few blocks from the WTC, trying to get a demo working
on a Compaq iPaq running Plan 9 in preparation for a trade show in San
Diego a day or two later. That, of course, never happened.

        - Dan C.


-rob
>
>
> On Fri, Sep 9, 2022 at 8:29 AM Dave Horsfall <dave@horsfall.org> wrote:
>
>> https://www.timeanddate.com/on-this-day/september/9
>>
>> ``Unix time or Unix epoch, POSIX time or Unix timestamp, is a time system
>>   that measures the number of seconds since midnight UTC of January 1,
>> 1970,
>>   not counting leap seconds. At 01:46:40 UTC on September 9, 2001, Unix
>> time
>>   reached the billionth second timestamp.''
>>
>> Hard to believe that it was that long ago...
>>
>> -- Dave
>>
>

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* [TUHS] Re: Happy birthday, Unix timestamp!
  2022-09-08 22:28 [TUHS] " Dave Horsfall
@ 2022-09-08 23:48 ` Rob Pike
  2022-09-09  0:11   ` Dan Cross
                     ` (2 more replies)
  2022-09-09  3:29 ` Seth Morabito
  1 sibling, 3 replies; 9+ messages in thread
From: Rob Pike @ 2022-09-08 23:48 UTC (permalink / raw)
  To: Dave Horsfall; +Cc: The Eunuchs Hysterical Society

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There was a delightful conference in Copenhagen celebrating that event, and
I was lucky enough to attend. The slides of my talk live here:
http://herpolhode.com/rob/ugly.pdf

I flew back the next day, September 10, 2011, and it was a beautiful clear
night with a stunning view of the city. We sat in the last row of the
plane, and had an unobstructed view of the trade towers as we landed near
midnight. We went home, fell asleep, and were woken by a phone call about
9am.

-rob


On Fri, Sep 9, 2022 at 8:29 AM Dave Horsfall <dave@horsfall.org> wrote:

> https://www.timeanddate.com/on-this-day/september/9
>
> ``Unix time or Unix epoch, POSIX time or Unix timestamp, is a time system
>   that measures the number of seconds since midnight UTC of January 1,
> 1970,
>   not counting leap seconds. At 01:46:40 UTC on September 9, 2001, Unix
> time
>   reached the billionth second timestamp.''
>
> Hard to believe that it was that long ago...
>
> -- Dave
>

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^ permalink raw reply	[flat|nested] 9+ messages in thread

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Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
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2022-09-09 18:53 [TUHS] Re: Happy birthday, Unix timestamp! Norman Wilson
  -- strict thread matches above, loose matches on Subject: below --
2022-09-09 12:06 Douglas McIlroy
2022-09-09 17:16 ` Andrew Hume
2022-09-08 22:28 [TUHS] " Dave Horsfall
2022-09-08 23:48 ` [TUHS] " Rob Pike
2022-09-09  0:11   ` Dan Cross
2022-09-09  4:24   ` Rob Pike
2022-09-11  0:09   ` Dave Horsfall
2022-09-09  3:29 ` Seth Morabito
2022-09-09  7:03   ` Michael Kjörling

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