Re: Y2K?

[dempson@actrix.gen.nz (David Empson)]

Mew <mew24e@hotmail.com> wrote:

> Only up to 2039 ? what we gonna do when we gonna use our old computers
> after this year ?

A fairly large number of old computers will have time problems during
the 2030s.

The standard time mechanism on most UNIX systems is based on a 32-bit
signed integer count of the number of seconds since an epoch (start
date) of 0:00:00, 1 January 1970.  The same mechanism is used as the
basic time mechanism in many implementations of the C language on other
platforms.

The maximum value of a 32-bit signed integer is 2147483647.  Ignoring
leap seconds, this works out to be 68 years, 18 days, 3 hours, 14
minutes and 7 seconds.

This means that affected systems will suffer a Y2K-like problem around
3:14:07, 19 January 2038 (give or take a few seconds), because the value
returned by the time() function will wrap around from 2147483647 to
-2147483648.

This problem can be fixed by updating the operating system and all
time-dependent applications to use a larger integer (e.g. 64 bits) as
the basis of the time mechanism.  We have just under 32 years left to
fix the affected systems, so better get started now!

Older hardware platforms which don't support 64 bit arithmetic will have
to synthesize it in software or be left behind and suffer problems,
assuming they are still working, of course!

Other platforms (e.g. Mac OS 9 and earlier, and various versions of
Windows) are also likely to suffer from "out of range" errors in their
time representations, but I'm less familiar with the specific details.

There are other time-related issues which crop up from time to time
(pardon the pun).  For example, the US and some states in Australia have
apparently changed their rules for Daylight Saving so the start and end
dates are changing from some point in 2006.  The latest version of Mac
OS X (10.4.5) has been updated to deal with this change, but anyone
running an older OS version in the affected countries will not do an
automatic daylight saving change at the correct point, and will have an
"out by one hour" error in any calcualtions involving UTC/GMT for the
duration of the period in which the rule differs from the old one.  The
same applies to every other operating system with support for automatic
daylight saving changes and time zone conversions (including Windows 95
and later, and all Unix and Linux systems).

Computers outside the countries/states in question will only be affected
if they need to calcaulte the local time in one of the affected areas
for some reason (e.g. a world clock).

Luckily the Apple II is relatively immune to this particular problem.
:-)

-- 
David Empson
dempson@actrix.gen.nz