Or you could simply check if it's time do to whatever you need to do...
The Time Alarms is a very nice library, but it's very easy to do the same only with the Time library, and the maintance are alot easier when you made all the code...
if (hour() == 12 && minute() == 0 && second() == 0) {
// answer the door
}
Or maybe, depending on what you really want to do you could even use millis() that is an arduino based "clock", which resets everytime you reset the arduino.
if (millis() == 10000) {
// answer the door
}