Another example is related in the story of the "Companions of the Cave" related in Surat al-Kahf.
Allah relates the story of young men who were compelled to take refuge from the cruel tyranny of the emperor of the time in a cave. It is related that they fell asleep and were woken up after years of sleep. The related verses follow:
When the young men took refuge in the cave and said, "Our Lord, give us mercy directly from You and open the way for us to right guidance in our situation." So We sealed their ears with sleep in the cave for a number of years. (Surat al-Kahf: 10-11)
That was the situation when we woke them up so they could question one another. One of them asked, "How long have you been here?" They replied "We have been here for a day or part of a day." They said, "Your Lord knows best how long have you been here. Send one of your number into the city with this silver you have, so he can see which food is purest and bring you some of it to eat. But he should go about with caution so that no one is aware of you." (Surat al-Kahf: 18-19)
The Qur'an does not explain exactly how much time the young men spent in the cave. Instead, the duration of this period is implied by the words "for a number of years." People’s guess at this period however was rather high: 309 years. Allah says: