my test result
command:uptime
show 4:15pm up 21:36, 2 users, load average: 0.00, 0.00, 0.00
run:
uptime | \
perl -ne '/.*up (\d+) days, +(\d+)
\d+),.*/; $total=((($1*24+$2)*60+$3)*60);
$now=time(); $now-=$total; $now=localtime($now); print $now,"\n";'
result:Fri Apr 17 16:16:50 2009
command:date
Fri Apr 17 16:17:22 EAT 2009