tai_pack doesn't give me the correct result

I'm a newbie C programmer, and I'm trying to learn how to use the TAI
library. I wrote the following program to practice with:

#include <stdio.h>
#include "caltime.h"
#include "tai.h"

main() {
	struct caltime m;
	struct tai t;
	char s[TAI_PACK];
	int i;

	caltime_scan("2003-02-25 12:00:00 +0000",&m);
	caltime_tai(&m,&t);
	tai_pack(s,&t);
	for (i=0; i < TAI_PACK; i++) printf("%02x ",s[i]);	
	printf("\n");
}


After I compile and run this, I get the following output:

40 00 00 00 3e 5b 5a ffffffca

I can see that the first 7 bytes look correct, but I don't understand
why the 8th byte looks wrong. Can anyone spot any obvious mistakes in
my code, or my understanding of the TAI label?

-- 
Anand Buddhdev
http://anand.org