[TUHS] Unix half a billion seconds old in 1985

Ken Thompson ken at google.com
Mon Nov 5 13:16:35 AEST 2018


unix time was originally measured in
ticks (60th of a second). alas, 2^32
only allows between 2 and 3 years.

so, we ran for 2 years and ended
up facing big problem in the 3rd.
our solution was to read all files
and all backup tapes and subtract
one year from all dates and move
the epoch up a year. we didnt mind
since dectapes (our backup tapes)
had to be rewritten to keep the bits
from rotting.

we did it again the next year and
when disaster was facing us on
the 4th year, we went to seconds.

it shows how much we bet on the
longevity of unix.


On Sun, Nov 4, 2018 at 4:42 PM, Bakul Shah <bakul at bitblocks.com> wrote:
> On Sun, 04 Nov 2018 15:44:37 -0700 Warner Losh <imp at bsdimp.com> wrote:
>>
>> On Sun, Nov 4, 2018 at 2:35 PM Dave Horsfall <dave at horsfall.org> wrote:
>>
>> > UNIX was half a billion (500000000) seconds old on Tue Nov  5 00:53:20
>> > 1985 GMT (measuring since the time(2) epoch).
>> >                 -- Andy Tannenbaum
>> >
>> > Hmmm...  According to my rough calculations, it hit a billion (US) seconds
>> > around 2000.
>> >
>>
>> It's over a billion and a half today:
>> % date +%s
>> 1541371441
>
> Strictly speaking Unix wasn't born on Thu Jan 1 UTC 1970, right?
> dmr says this in "The Evolution of the Unix Time-Sharing Sytem":
>
>   Although it was not until well into 1970 that Brian
>   Kernighan suggested the name `Unix,' in a somewhat
>   treacherous pun on `Multics,' the operating system we know
>   today was born.
>
> I wonder if how many unix programmers were born on Thu Jan 1
> UTC 1970.  Linus comes close.


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