I have heard for a long time that in maybe 2039 Unix will no longer be useable due the length of the date value. Anyone know anything about this?

This is down to the time_t type being 32 bits on 32 bit machines.

It measures time in seconds from the start of the epoch, 1st Jan 1970.

So 64 bit machines are not affected, you need to confirm how file systems store dates. There needs to be a binary level change to make time_t a "long long" or a 64 bit number.

For 32 bit time_t values
produces this value:

Mon Jan 18 20:14:07 2038

If you add one second to that lt variable the result on my HPUX box is:

Fri Dec 13 13:45:52 1901 -- a time in the past

Hi Jim ..

That is great i made thi is my unix Hp machine and executed
#include <time.h>

int main()
{
time_t lt=0x7fffffff;

printf(asctime(localtime(&lt)));

printf(asctime(localtime(&lt) + 1 ));

return 0;
}


i got the result as
Mon Jan 18 22:14:07 2038
and
Sun Jan 0 00:00:00 1900

what is

time_t lt=0x7fffffff;

please explain ..

Thanks in advance,
Arun .

It's hex for the largest positive number a signed 32bit number can represent. -- sort of the end of time for 32 bit time_t numbers

2147483647