Argthtjtr

Vivekananda states the difference between sleeping and Samadi in the following lines from CHAPTER VII: DHYANA AND SAMADHI of Raja Yoga. In short, sleeping does not cause any change in knowledge but Samadi state changes knowledge.

How, for instance, do we know that a man in Samadhi has not gone below consciousness, has not degenerated instead of going higher? In both cases the works are unaccompanied with egoism. The answer is, by the effects, by the results of the work, we know that which is below, and that which is above. When a man goes into deep sleep, he enters a plane beneath consciousness. He works the body all the time, he breathes, he moves the body, perhaps, in his sleep, without any accompanying feeling of ego; he is unconscious, and when he returns from his sleep, he is the same man who went into it. The sum total of the knowledge which he had before he went into the sleep remains the same; it does not increase at all. No enlightenment comes. But when a man goes into Samadhi, if he goes into it a fool, he comes out a sage.

Time for sleeping depends on the sleeping habits of the person and on average one needs to sleep around at least 6 days in general. Any person can wake the sleeping person or the person may voluntarily wake up after their feeling of sleepiness went.

I have two doubts:

1. Who decides the time of staying in Samadi state? Is it in hands of the person in Samadi or is there any fixed time to stay in Samadi state?




2. Can another person wake up a person who is in Samadi state?

I am partially answering the question. I am answering only question number 2 viz:

Can another person wake up a person who is in Samadhi state?

Yes, it is possible. In biographies of Sri Ramakrishna Paramhamsa, I have read that on few occasions, by chanting sacred formulas (Bija/Mula Mantras) into his ears, he was successfully brought back to normalcy from the state of Samadhi.

This is mentioned in the short biography of his consort Sri Sarada Devi - Holy Mother.

The Holy Mother lived at Dakshineswar for another year after this
worship. But what an ordeal it was to stay with Sri Ramakrishna! Often
he would fall into samadhi and pass the whole night in that state, and
she had an anxious time. One night Sri Ramakrishna was so deep in
samadhi that one might take him to be dead. In great anxiety the Holy
Mother had to send information to others for help. It was a long time
before he could be brought down to the normal plane by the repeated utterance
of sacred mantras. After regaining external consciousness, when Sri
Ramakrishna knew all that had happened, he understood how the Holy
Mother was passing night after night in sleepless anxiety on his
account.

Another instance, where mother Sarada herself had to be brought back from Samadhi by using the same method, is as follows:

At Vrindavan she would be so much absorbed in japa and meditation that
she was not conscious at the time that flies were making sores on her
face. Sometimes in an exalted mood she would go alone to the sandy
banks of the Yamuna, from where her companions had to bring her back.
It is said that at Kala Babu’s house she was so absorbed in samadhi that she could be brought down to the earthly plane only with
considerable effort, by repeatedly uttering the name of the Lord in
her ears.

Yet another incident about Ramakrishna being brought back from a Samadhi by use of Mantras is mentioned in Ramakrishna's short biography here.

Finally Sri Ramakrishna said, ‘I hear that you have seen God, so I
have come to hear about it.’ The ensuing conversation held Keshab and
his followers under its spell. Sri Ramakrishna then sang a song of
Kali the Mother with his usual fervour, in the course of which he fell
into Samadhi. Hriday brought his uncle back to ordinary consciousness
by chanting the sacred word Om in his ears. Sri Ramakrishna’s face
was beaming with a divine radiance. A torrent of inspiring words
flowed, which went straight to the hearts of the listeners.

So, it is definitely possible, provided the other person knows what to do and how to do.