hibernate med rtcwake: 2 timer forkert

Jeg har et script til at få nogle Ubuntu æsker til at gå i dvale kl 17:00 og vågne igen kl 07:00 - problemet er bare at hvis jeg angiver:
"suspend_until_script 07:00" vågner den først kl 09:00... hvad gør jeg forkert:

Script (hentet fra http://askubuntu.com/questions/61708/automatically-sleep-and-wake-up-at-specific-times):

#!/bin/bash

# Auto suspend and wake-up script
#
# Puts the computer on standby and automatically wakes it up at specified time
#
# Written by Romke van der Meulen <redge.online@gmail.com>
# Minor mods fossfreedom for AskUbuntu
#
# Takes a 24hour time HH:MM as its argument
# Example:
# suspend_until 9:30
# suspend_until 18:45

# ------------------------------------------------------
# Argument check
if [ $# -lt 1 ]; then
    echo "Usage: suspend_until HH:MM"
    exit
fi

# Check whether specified time today or tomorrow
DESIRED=$((`date +%s -d "$1"`))
NOW=$((`date +%s`))
if [ $DESIRED -lt $NOW ]; then
    DESIRED=$((`date +%s -d "$1"` + 24*60*60))
fi

# Kill rtcwake if already running
sudo killall rtcwake

# Set RTC wakeup time
# N.B. change "mem" for the suspend option
# find this by "man rtcwake"
sudo rtcwake -l -m mem -t $DESIRED &

# feedback
echo "Suspending..."

# give rtcwake some time to make its stuff
sleep 2

# then suspend
# N.B. dont usually require this bit
#sudo pm-suspend

# Any commands you want to launch after wakeup can be placed here
# Remember: sudo may have expired by now

# Wake up with monitor enabled N.B. change "on" for "off" if
# you want the monitor to be disabled on wake
xset dpms force on

# and a fresh console
clear
echo "Good morning!"