Establecer el tiempo relativo usando la línea de comando

Para establecer la fecha, debe iniciar sesión como root (o su/sudo...)

echo "Time 1 hour ago ... $(date -d "$(date +%F\ %T) 1 hour ago")"
echo "Time now .......... $(date  +%F\ %T)"
echo "Time in 1 hour .... $(date -d "$(date +%F\ %T) 1 hour")"

sudo date +%F\ %T -s "$(date -d "$(date +%F\ %T) 1 hour")"
echo "Adjusted time ..... $(date  +%F\ %T)"

sudo date +%F\ %T -s "$(date -d "$(date +%F\ %T) 1 hour ago")"
echo "Re-adjusted time .. $(date  +%F\ %T)"

salida:

Time 1 hour ago ... 2012-04-16 21:31:53
Time now .......... 2012-04-16 22:31:53
Time in 1 hour .... 2012-04-16 23:31:53
[sudo] password for .... 
Adjusted time ..... 2012-04-16 23:31:53
[sudo] password for  .... 
Re-adjusted time .. 2012-04-16 22:31:53