Ethernet Shield using Alarms for Garduino

Could you give an example how to call a determined function at a certain time at loop?

int waterHour = 5;
int waternMin = 0;
int waterSec = 0;
bool watered = false;

void loop()
{
   if(hour() == waterHour && minute() == waterMinute && second() == WaterSecond && !watered)
   {
       Water();
       watered = true;
   }
   else
       watered = false;
}