Hi Bert.

The point that confussed me more was that the chip was not set by me. It was set by Maxim or another person far far away from me in a different time zone, before winter time.

As you can see by the attached picture above, it has 0-1 seconds difference from my PC! Amazing. There must be a trick.

I found this C program but could not understand what really does.

Code:
void loop(void) {
  byte i;
  byte present = 0;
  byte data[8];
  byte addr[8];
  uint32_t timestamp;
  int seconds = 0;

  if ( !ds.search(addr)) {
	//Serial.print("No more addresses found.\n");
	ds.reset_search();
	delay(500);  // for readability
	return;
  }

  present = ds.reset();
  ds.select(addr);
  ds.write(0x66,1);   // read RTC
  for ( i = 0; i < 5; i++) {
    data[i] = ds.read();
  }
	timestamp = data[1];
	timestamp = timestamp << 8;
	timestamp |= data[2];
	timestamp = timestamp << 8;
	timestamp |= data[3];
	timestamp = timestamp << 8;
	timestamp |= data[4];
Serial.println(timestamp);
delay(1000);
}
Ioannis