The fairy-tale in many countries has the tale of strange time experience. The most famous tale of this type in Japan is "Urashima Taro". He went to Ryugu-palace and stayed only two months. But when he returned to his country, he could not find his home and acquaintance. At last he knew that his stay in Ryugu was not two months but two hundred years.

We have occasionally really such experience as the following. When we traveled for a long time, the memory concerning our country interrupts at that starting time. And when we came back, for example five years after, we connect directly the homecoming time with that preceding fresh memory of five years before. Then our baby who was yesterday one year old in home at starting time of travel, becomes today suddenly six year old child.

We feel that our travel might be only two days' travel, yesterday we started and today come back, nevertheless at the same time it was the five years progress of our country's time too. And so we must guess that one day in foreign country where we traveled is equal with five years in our country. Urashima's experience is exaggerated but is not fiction.