Introduction
Those who know the supreme Divine attain that Supreme by passing away from the world during the influence of Agni, the fire-god, during light or at an auspicious moment of the day, also during the fortnight of the waxing moon or during the six months that the sun travels in the north, referred to as uttarāyaṇaṁ.
Understand, these are not chronological calendars. If it were a chronological calendar, then at uttarāyaṇaṁ time, all of us can commit suicide and be done with it, that's all! But that is not what is meant here. All these things have metaphorical meanings. When He says uttarāyaṇaṁ, Kṛṣṇa means when our mind is totally balanced and when we are not agitated.
In the Mahābhārat war it is said that Bhīśma Pitāmaḥ waits for uttarāyaṇaṁ to leave the body. Don't think he waited for January. He waited until his mind settled down from the agitations and incompletions, and he establishes himself in the space of completion.
He had fallen in battle and was lying down on a bed made of arrows. He must have felt agitated. He must have felt, 'My grandson, whom I taught everything, for whom I did everything, did this to me.' He would have been disturbed. So he waited until the agitation settled down. That is what is meant by the words, 'he was waiting for uttarāyaṇaṁ.'
Don't think these are chronological concepts. They are psychological. If it were chronological, then do you think that the millions of people who die in those six months become enlightened? Enlightenment is not an accident! It is a pure conscious choice. So be very clear, when He says agnir jyotir ahaḥ śuklaḥ.
He means if we are conscious ... agnir jyotir ... means when your being is conscious ... when your being is fully alive, awakened, naturally you go up. (śuklaḥ means going above, kṛṣṇa means going down). If we live throughout life centered on the eyes, our energy leaves through the eyes. At the last moment, we open the eyes and the soul leaves. If we live throughout life centered on the tongue, eating, our mouth opens and the soul leaves through it. So if we live throughout life centered on higher consciousness, our energy leaves through the sahasrāra, the crown cakra, the energy center on the top of our head.