diff --git a/machine_poweroff.sh b/machine_poweroff.sh
index 92ed8ee..1a00cef 100755
--- a/machine_poweroff.sh
+++ b/machine_poweroff.sh
@@ -7,40 +7,61 @@ usage() {
 
 cat<<EOF
 
-   Usage: $(basename $0) YYY-MM-DD
+   Usage: $(basename $0) YYYY-MM-DD
 
    $(basename $0) - Scripts shuts down this machine if the given date is the actual date.
 
-                 The most common practice is, to use this script as cronjob.
+                         The most common practice is, to use this script as cronjob.
 
 EOF
 
 exit 1
 }
 
-[ $# -ne "1" ] && usage "wrong number of arguments"
+isValidDate() {
+    DATE="${1}"
+
+    # Autorized separator char ['space', '/', '.', '_', '-']
+    SEPAR="([ \/._-])?"
+
+    # Date format day[01..31], month[01,03,05,07,08,10,12], year[1900..2099]
+    DATE_1="((([123][0]|[012][1-9])|3[1])${SEPAR}(0[13578]|1[02])${SEPAR}(19|20)[0-9][0-9])"
+
+    # Date format day[01..30], month[04,06,09,11], year[1900..2099]
+    DATE_2="(([123][0]|[012][1-9])${SEPAR}(0[469]|11)${SEPAR}(19|20)[0-9][0-9])"
+
+    # Date format day[01..28], month[02], year[1900..2099]
+    DATE_3="(([12][0]|[01][1-9]|2[1-8])${SEPAR}02${SEPAR}(19|20)[0-9][0-9])"
+
+    # Date format day[29], month[02], year[1904..2096]
+    DATE_4="(29${SEPAR}02${SEPAR}(19|20(0[48]|[2468][048]|[13579][26])))"
+
+    # Date 29.02.2000
+    DATE_5="(29${SEPAR}02${SEPAR}2000)"
+
+    # Match the date in the Regex
+
+    if [[ "${DATE}" =~ ^(${DATE_1}|${DATE_2}|${DATE_3}|${DATE_4}|${DATE_5})$ ]] ; then
+      return 0
+    else
+      return 1
+   fi
+}
+
+[ $# -ne "1" ] && usage "Wrong number of arguments"
 
 _date=$1
 
 IFS='-' read -a _val_arr <<< "$_date"
 
-declare -i _year="${_val_arr[0]}"
-declare -i _month="${_val_arr[1]}"
-declare -i _day="${_val_arr[2]}"
+__year=${_val_arr[0]}
+__month=${_val_arr[1]}
+__day=${_val_arr[2]}
 
-if [[ $_month -lt 1 ]] || [[ $_month -gt 12 ]]; then
-   usage "Wrong date format."
-fi
-
-if [[ $_day -lt 1 ]] || [[ $_day -gt 31 ]]; then
-   usage "Wrong date format."
-fi
-
-if [[ $_year -lt $(date +%Y) ]] ; then
-   usage "Wrong date format."
+if ! isValidDate "${__day}-${__month}-${__year}" ; then
+	usage "Invalid date: ${_date}"
 fi
 
 [[ "$(/bin/date +%Y-%m-%d)" == "$_date" ]] && /sbin/poweroff
-#[[ "$(/bin/date +%Y-%m-%d)" == "$_date" ]] && echo "ok: $_date " || echo "failed: $_date"
 
 exit 0