much thanks. The A Lange function is advance a day by the push of a button at the 10 o'clock position, all synchronised. For Patek, to advance a day, you can advance the hour and minute hand 24 hours, achieve the same thing but with much more effort. Some forum memebers are saying there is a button at the 58th minute on the 3970/5970 to do exactly like the Lange does. Don't know who is right.