tm.sh

#!/bin/sh

enabled=`/usr/bin/defaults read /Library/Preferences/com.apple.TimeMachine AutoBackup`

if [ "$enabled" == "1" ];then
    lastBackupTimestamp=`date -j -f "%a %b %d %T %Z %Y" "$(/usr/libexec/PlistBuddy -c "Print Destinations:0:SnapshotDates" /Library/Preferences/com.apple.TimeMachine.plist | tail -n 2 | head -n 1 | awk '{$1=$1};1')" "+%Y-%m-%d %H:%M:%S"`
    echo "$lastBackupTimestamp"
else
    echo "<result>Disabled</result>"
fi

echo "$lastBackupTimestamp" > ~/Desktop/tmDate.txt