Everything that is born has to die, that is the law of material nature. As soon as a man is born, he dies at every moment. Every birthday reduces our fixed life-span by one year and brings us closer to death. Thus death, in the form of time, is devouring every living entity at every moment, but the last stroke is called death itself. That death is non other than the Lord in His impersonal feature as the time factor.
The Srimad-Bhagavatam compares time to the deadly sharp blade of a razor. Because time imperceptibly devours the duration of life of everyone, one must carefully use one's life properly. Who is awake when everything is asleep? - it is time. This time factor is unreversable, unchangeable and limitless, and it works as the agent of the Supreme Lord for the process of material creation [SB 3.10.11].
Time, the all devouring death Kala is the time factor with past, present and future, and represents the supreme Lord in His unmanifested impersonal feature. Eternal time is the primeval cause of material natures manifestation. No one knows where time began and where it ends, and it is time only which can keep a record of the universal creation, maintenance and annihilation. Therefore time has no beginning and no end. Under the influence of eternal time the cosmic manifestation is created, maintained and annihilated at regular intervals.
Since Kala, the time factor, is eternal the process of material creation is not a one-time affair but a repeated process which goes on eternally. This process of repeated creation and annihilation is described in the Srimad-Bhagavatam as follows: "The present cosmic manifestation as it is now, was the same in the past, and it will continue in the same way in the future also" [SB 3.10.13].
The Bhagavad-gita similarly states that this universal manifestation is created and annihilated perpetually. In chapter nine, text eight it is said that the universal manifestation as it is created now and as it will be destroyed later on, so also existed in the past and again will be created, maintained and destroyed in due course of time. Therefore, the systematic activities of the time factor are perpetual and eternal and cannot be stated to be false. The manifestation of material nature is temporary and occasional, but not false as claimed by the mayavadi philosophers. The scheduled creation and annihilation take place in terms of the Supreme will. They are situated as the objective manifestation of the Lord's external energy.
The controlling time has different dimensions in relation to particular physical embodiments. There is a time for atomic dissolution and a time for the universal dissolution. There is a time for the annihilation of the body of the human being, and there is a time for the annihilation of the universal body.
The complete universe is a manifestation of varieties of entities, beginning from the atoms up to the gigantic universe itself, and all is under the control of the Supreme Lord in His form of Kala, or eternal time.
Time passes differently according to one's situation in the cosmos. Lord Brahma lives for one hundred years, but his twelve hours consist of one thousand cycles of four ages (yugas): Satya, Treta, Dvapara and Kali. A single cycle of Kali, the shortest, yuga, corresponds to 4,320,000 solar years. These four yugas, rotating a thousand times, comprise one day of Brahma, and the same number comprise one night. Brahmä lives one hundred of such "years" and then dies. These "hundred years" by earth calculations total to 311 trillion and 40 billion earth years.
The duration of life is one hundred years in the present age of Kali-yuga; one thousand years in Dvapara-yuga; ten thousand in Treta-yuga; and one hundred thousand years in Satya-yuga. Time is relative to the kind of body one occupies. While Brahma's one hundred years equal 311 trillion of our years, an insect's one hundred years might come to no more than one of our days or less. And on the heavenly planets ruled by Lord Indra, one day equals six of our earthly months.
The material creation seems to be separated from the Lord as external energy due to this time factor which is the unmanifested, impersonal feature of the Supreme Lord. This can be understood by the example of a tape recorder. It is something like the tape recorded voice of a person who is now separated from the voice. As the tape recording is situated on the tape, so the whole cosmic manifestation is situated on the Lord's material energy and appears separate by means of kala.
The material manifestation is therefore the objective manifestation of the Supreme Lord and exhibits His impersonal feature which is so much adored by impersonalist philosophers. Mayavadis say that this manifestation of material nature [prakriti] is false, but according to the Vaisnavas and the philosophy of Bhagavad-gita, this is not so. The manifestation of the world is not accepted as false; it is accepted as real, but temporary. This material manifestation takes place at a certain interval, stays for a while and then disappears.
Material nature [prakriti] is ever existing in its subtle form as the energy of the Lord, but is sometimes manifests this non-existent or temporarily existent nature, the cosmos [SB 3.26.9]. In Bhagavad-gita the Lord refers to this as 'my prakriti'. This prakriti consists of the three modes of material nature: sattva-guna, raja-guna, tama-guna, which stand for equilibrium, motion and inertia. The interaction of material nature takes place when the equilibrium of the three gunas is disturbed by the time factor. Therefore, kala or eternal time is the primeval cause of the interactions of the three modes of material nature. Time creates, time maintains, time destroys, and this time factor is non other than the Lord.
Time controls and subdues all embodied beings. Anyone can easily see and experience that material bodies undergo six changes: birth, growth, maintenance, reproduction, decay and death. Whether we like it or not, every rising and setting of the sun brings us closer to inevitable death. The rise and fall of civilizations follow the same pattern, and their Taj Mahals, Chateaus de Versailles and pyramids stand as pathetic reminders that time and tide wait for no man.
Chanakya Pandit, a great scholar, says that even a slight fraction of time cannot be purchased with millions of gold coins, and therefore even a moment of time lost without reaching the goal of life must be calculated as the greatest loss in life.
Since time represents the Supreme Lord, using time to search for the Absolute Truth is the best practical use of time. Otherwise one's life is uselessly wasted in due course of time.