Solaris

date +%s -d "01/01/2000 00:00:00"

$ touch -t 200001010000.00 somefile
$ perl -e 'printf "%d\n", ((stat(shift))[9]); ' somefile
946702800
$ perl -e 'print scalar localtime(shift),"\n"' 946702800
Sat Jan  1 00:00:00 2000
$

/usr/bin/truss /usr/bin/date 2>&1 | /usr/bin/awk '/^time/ {print $NF}'

perl -e 'use Time::Local; print timelocal("00","00","00","01","01","2000"),"\n";'

#!/usr/sbin/dtrace -qs

tick-1sec
{
        printf("%d seconds since the epoch\n", `time);
        exit(0)
}