Lord Caitanya Mahaprabhu appears in ''one'' Kali-yuga out of every 1000 with His great Sankirtan Movement.

That is "once" every 8 billion 640 million human years or "once" in Brahma's 24 hour day during the daytime.

The Sankirtan Movement of Lord Caitanya Mahaprabhu is a great gift to the world and a very rare event.

Many do not realize how rare Lord Caitanya's appearance is in this individual universe as He comes only "once" in a 24 hour day and night of Lord Brahmā which is "once" every 8 billion 640 million human years.

That is once out of every 1000 Kali-yugas in the cycle of Maha-yugas that happen during Lord Brahma's daytime (sunrise to sunset)

There are 4 yugas in a Maha-yuga (Satya, Treta, Dvarpara, Kali-yuga)

There are no Maha-yugas during Lord Brahma's night (sunset to sunrise) when a partial annihilation happens while Brahma sleeps.

Lord Brahma's night of sleeping is called the "Night of Brahma" and there are no cycles of yugas during that ''sleeping time of Brahma'' as already explained.

Brahma's night-time is 4 billion 320 million human years long, and his day-time is also 4 billion 320 million human years making a full 24 hour day 8 billion 640 million human years long.

As said above, Lord Caitanya appears in one Kali-yuga out of every one thousand Kali-yugas

The length of the 4 yugas (a Maha-yuga) is 4 million 320 thousand human years.

Multiply that by 1000 (Maha-yugas) and that approximately equals 4 billion 320 million human years.

Then add another 4 billion 320 million years for Brahma's night time period (the same amount of time as the day time) when Brahma rests while a partial annihilation goes on.

So it is important to understand there are no Maha-yugas during Lord Brahma's night-time.

Therefore, we can understand that Lord Caitanya's appearance is very, very rare as He only comes once in over that enormous period of time (8 billion 640 million human years)

Krsna also comes "once" out of every 1000 Maha yugas at the end of a Dvarpara-yuga over a period of 24 hours of Brahma.

Krsna appears in His original body at the end of every 1000 Dvarpara-yuga, just before Lord Caitanya's appearance also once out of every 1000 Kali-yugas.

In this rare Kali-yuga there there is also a 10,000 years Golden Age of the Sankirtan Movement of Lord Caitanya Mahaprabhu (the congregational chanting of the Hare Krsna Maha mantra)

The previous 999 Kali-yugas had no Lord Caitanya or Golden Age of Sankirtan.

The Four Yugas.

The four yugas make up a cycle called Divya-yuga or Maha-yuga, which lasts 4,320,000 human years.

One thousand of these yugas equal one day-time period from Sunrise to Sunset of Brahma 24 hour day, which is called a kalpa and another one thousand makes up a night.

Brahma's lifespan is 100 years of his time and 311 Trillion 40 billion years of our time.

SATYA YUGA - (sometimes also called krta-yuga): The golden age lasts 1,728,000 years. The process of self-realization in this yuga is meditation on Visnu. During this yuga the majority of the population is situated in the mode of goodness and the average life span at the beginning of the yuga is 100,000 years.

TRETA YUGA - Also called the silver age, lasts 1,296,000 years and the process of self realization is the performance of opulent yajnas(sacrifices). The average life span is 10,000 years and the godly qualities decrease one fourth compared to the Satya yuga.

DVAPARA YUGA - Or the bronze age, lasts 864,000 years and the process of self realization is the worship of the deities within temples. Godly qualities are reduced to 50% by now and the average life expectancy is only 1000 years.

KALI YUGA - The iron age of hypocrisy and quarrel lasts 432,000 years. Lord Krsna appeared in His original, transcendental form right before the beginning of a Kali-yuga at the end of Dvarpara-yuga in ''one day and night'' of Brahma which is every 1000 cycles of yugas.

The time span of the 1000 Maha-yugas takes 4 billion 320 million human years and is equal in time to the night of Brahma. Therefore there is no cycles of 4 yugas at night for 4 billion 320 million years.

Both Krsna in His original Form and Lord Caitanya do NOT appear in every Maha-yuga. Kṛṣṇa does not appear at the end of every Dvarpara-yuga and Lord Caitanya does NOT appear in every Kali-yuga as explained above. Lord Kṛṣṇa Himself in His original blackish color does not appear in every Dvāpara-yugas in a day of Brahma." (Caitanya Caritamrita Madhya 20.337)

Srila Prabhupada -“In Dvāpara-yuga the Personality of Godhead appears in a blackish hue. He is dressed in yellow, He holds His own weapons, and He is decorated with the Kaustubha jewel and the mark of Śrīvatsa. That is how His symptoms are described." 

(Caitanya Caritamrita Madhya 20.337)

Srila Prabhupada - "This is a quotation from Śrīmad-Bhāgavatam (SB 11.5.27). The śyāma color is not exactly blackish. Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura compares it to the color of the atasī flower. It is not that Lord Kṛṣṇa Himself appears in a blackish color in all the Dvāpara-yugas. In other Dvāpara-yugas, previous to Lord Kṛṣṇa’s appearance, the Supreme Lord appeared in a greenish body by His own personal expansion. This is mentioned in the Viṣṇu Purāṇa, Hari-vaṁśa and Mahābhārata."(Bhagavad Gita As It Is Preface)

Some references in sastra also say 8 billion 640 billion while in other places it says 8 billion 600 million for example. 

Srila Prabhupada - ''Our only purpose is to present this Bhagavad-gītā As It Is in order to guide the conditioned student to the same purpose for which Kṛṣṇa descends to this planet once in a day of Brahmā, or every 8,600,000,000 years.''(Caitanya Caritamrta Adi 3.10)

Srila Prabhupada - "In the term of Vaivasvata Manu, during which Lord Caitanya appears, it says first Lord Kṛṣṇa appears at the close of the Dvāpara-yuga of the twenty-eighth divya-yuga, and then Lord Caitanya appears in the Kali-yuga of the same divya-yuga. Lord Kṛṣṇa and Lord Caitanya appear once in each day of Brahmā, or once in fourteen manvantaras, each of seventy-one divya-yugas in duration. From the beginning of Brahmā’s day of 4,320,000,000 years, six Manus appear and disappear before Lord Kṛṣṇa appears. Thus 1,975,320,000 years of the day of Brahmā elapse before the appearance of Lord Kṛṣṇa. This is an astronomical calculation according to solar years."(Caitanya Caritamrta Adi 3.10)

Note - There is also 4,320,000,000 years in Brahma' inactive sleeping night where there are no cycle if yugas so a night and day together is 8,640,000,000 years.

Sometimes one will notice figures in some purports are a little different from other purports in Prabhupada's Books, for example here a day and night of Brahma is 8 billion 640 million were as in the preface of Bhagavad gita it says 8 billion 600 million.

Srila Prabhupada - "The undifferentiated Absolute Truth, the original Supreme Personality, Lord Śrī Kṛṣṇa, incarnates in this material world once in every day of Lord Brahmā—that is once every 8,640,000,000 solar years—to shower His mercy upon both His surrendered devotees and the atheistic nondevotees. He protects His devotees and slays the atheistic demons, thus giving the latter troublesome release, so to speak, in impersonal liberation."(Renunciation Through Wisdom 4.5)

Srila Prabhupāda - "Oh. Anyway, I give you the right figure, four million, according to American or English calculation, (laughter) 4,300,000 years and multiply it by one thousand. Then what it comes according to English calculation? That is twelve hours. And add again twelve hours, night. Then eight billion? So Kṛṣṇa comes after this period. (laughter) In one day, after one day of Brahma, He appears."

Devotee - "Śrīla Prabhupāda, does Lord Caitanya Mahāprabhu also appear every day of Brahma?"

Srila Prabhupāda - "Yes, following Kṛṣṇa. Kṛṣṇa comes in the Dvāpara-yuga. There are four periods of each yuga: Sattva, Tretā, Dvāpara, Kali. So Kṛṣṇa comes at the end of Dvāpara-yuga, and Caitanya Mahāprabhu comes in the Kali-yuga." (Lecture on SB 6.1.3, Melbourne, May 22, 1975)

Conclusion.

So if one does the maths there is 1000 Maha-yugas in the day time of Brahma that equals 4 billion 320 million human years and there is another 4 billion 320 million human years in the night time of Brahma's day where he sleeps and creates no cycle of yugas.

Therefore a day-night of Lord Brahma adds up to 8 billion 640 million human years.

There are 4,320,000 human years in a Maha Yuga multiply that by 1000 (that equals 4 billion 320 million years) then add another 4 billion 320 million years for Brahmas night of sleep where no yugas are created and we understand that Lord Caitanya and Kṛṣṇa's appearance in one ''day and night'' of Brahma is very, very rare.

Compiled by Gauragopala dasa ACBSP