Our (US) $s at work.

[Joel Jaeggli]

On Mon, 1 Aug 2005, Mike McCarty wrote:

> Craig White wrote:
>> On Mon, 2005-08-01 at 14:40 -0500, Mike McCarty wrote:
>> 
>>> Dotan Cohen wrote:
>>> 
>>>> On 8/1/05, Mike McCarty <mike.mccarty at sbcglobal.net> wrote:
>>>> 
>>>> 
>>>>> Would you please explain to me how my machine automagically knows it
>>>>> needs to change the content of a file on its disc when the legislature
>>>>> makes a change to the way DST works?
>>>>>

it doesn't so millions of pc have to be patched or updated.


<snip>

>
> How does one get through to you? I ALREADY KNOW HOW TO USE YUM. I KNOW
> HOW IT WORKS. READ WHAT I WROTE.
>
> You again responded to what you read rather than what I asked.
>
> Is English your first/primary language?
>
> The purpose of my questions is to point out that the fellow wanted to
> know how to update the files *HIMSELF* and the only responses he's
> getting are from people like you who cannot/will not respond to the
> question AS ASKED.
>
> The answer to my question, AS ASKED, is "It is impossible for your
> machine automatically to change the configuration files by itself
> when your local government passes a new ordinance."
>
> And the answer to the OP's question is so far not yet given.

The magic that switches unix style sysems for regular to  daylight saving 
and back is the timezone description file typically /etc/localtime which 
is in tzfile format.

for info on the format look at:

man 5 tzfile

for a treatment of the functions in libc that support this. and actually 
output the time:

man localtime

For systems where the system clock is utc/gmt (the right way to set your 
time imho) the tzset function derives local time from the timezone file 
set in your environment (which practically speaking means everyone on
the machine can have a different localtime represented (or more than one).

man tzset

unix/posix time is measured as the number of seconds elapsed since 0000 
utc jan 1 1970. the unix day increases by exactly 86400 second per day 
plus the occasional discontinious leap second to keep the unix day in sync 
with the earths rotation. unix time is represented in your kernel as a 
signed 32 bit int and all time on a posix system is fundamentaly derived 
from unix time.

see:

http://en.wikipedia.org/wiki/Unix_time

for a more complete treatment on posix time.

joelja

> Mike
>

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Joel Jaeggli  	       Unix Consulting 	       joelja at darkwing.uoregon.edu
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