As far as I know, there are two major Buddhist prophetic cycles that may be related to the 21st century: the 2,500-year mappo cycle  and the Kalachakra prophecies.
The word mappo (more correctly, mofa) derives from the Chinese 末法, meaning “the end of dharma,” and refers to the last of three ages, commencing with the death of the Buddha, estimated (according to current scholarship) to correspond to the year 405 BCE. In the Sutra of the Great Assembly (Mahasamnipata Sutra), the three periods are further divided into five five-hundred year periods, the fifth and last of which was prophesied to be a time when the Buddhism of Shakyamuni would lose all power of salvation and a new Buddha would appear to save the people. This period would be characterized by unrest, strife, famine, and other natural disasters. The final millennium and century of this 2,500-year cycle represents the nadir of the first 2,500-year cycle of historical Buddhism, and the arising of a new current. Descriptions of the three periods also appear in other sutras. Since the Buddha died about 400 BCE, this means that the “new current” may be expected about 2100, corresponding very neatly both with the rise of the technological singularity (2045) and the future appearance of Shambhala according to the Kalachakra.
If one looks at historical Buddhism in the light of this theory, the following historical development may be seen:
- 400 BCE-100 CE: The death of the Buddha followed by the consolidation of the teachings in the Pali Canon; a period of establishment and consolidation; Outer Buddhism. This is the first half of the Age of the Righteous Law, characterized by salvation.
- 100 CE-600 CE: the Fourth Buddhist Council leading to the arising of the Greater Way (Mahayana) culminating in the appearance of Nalanda University; a period of expansion and differentiation; Inner Buddhism; culminating in the appearance of the “barbarian dharma.” 600 CE also corresponds to the prophesied “end of the sangha.” This is the second half of the Age of the Righteous Law, characterized by meditation.
- 600 CE-1100 CE: the rise of Vajrayana and Tibetan Buddhism culminating in the appearance of Padmasambhava; a period of intensification and realization; Secret Buddhism. This is the first half of the Age of the Counterfeit Law, characterized by reading, intoning, and the letter of the Law.
- 1100 CE-1600 CE: the appearance of the first Dalai Lamas; a period of preservation, consolidation, and externalization; beginning of decline. This is the second half of the Age of the Counterfeit Law, characterized by the worship of stupas and temples.
- 1600 CE-2100 CE: the full decline of Buddhism, with the promise of revival at the midpoint, at the point of greatest darkness. This is the Age of the Decay of the Law, characterized by strife and division.
- 2100 CE-2600 CE: the Dharma Transmission to the West (DTW); a period of renewal and revivification in the midst of great darkness.
According to this exegesis, then, the high point of historical Buddhism was reached in the ninth century of the Common Era, corresponding to Nalanda University and Padmasambhava, and the low point, the nineteenth century, corresponding to the revival of Sri Lankan Theravada Buddhism and the beginning of the Dharma Transmission to the West. Padmasambava’s sudden appearance in Tibet also occurred at the midpoint of the 2,500-year cycle, midway between the parinirvana of the Buddha and our own time.
In this context it is interesting to note that the advent of the Kali Yuga in 3102 BCE, which also corresponds to the advent of the current age of the Mayan cycle in 3114 BCE, plus 2,000 years, equals 5,000 years (2 x 2,500 years). The length of this age also corresponds quite well with the astrological precession of the equinoxes (roughly 26,000 years), culminating in the so-called “Age of Aquarius.” All of these theories appear to be consolidated and harmonized in the Buddhist chronology just presented.
The Kalachakra prophesies the advent of Shambhala 1,412 years after the advent of the Kalachakra era in 1012 CE (which also corresponds to the advent of the mappo), in 2424 CE, when spirituality and technology (technocracy) will converge in a new, global, post-Abrahamic civilization of the future (2424 – 1012 = 1,412. This is 412 years after 2012. Similarly, 1012 + 400, corresponding to the best current estimate of the parinirvana of the Buddha, = 1,412. Thus, the mappo began at the midpoint of this cycle). At that time, the world will be divided between the “barbarian dharma” and Buddhism. The barbarian dharma, about which we can only speculate since it is so far in the future, will then wage a war of final annihilation on the dharma, but its own karma will return upon it and destroy it, resulting in the advent of a planetary dharmic civilization that is identified with the end of the Kali Yuga. This constitutes an alternative chronology to the Hindu/Vedic view in which the Kali Yuga lasts for hundreds of thousands of years. The time from the advent of the Kali Yuga to the advent of Shambhala is therefore 5,525 years. The midpoint of this cycle is close to 400 BCE. The midpoint of the second half of this cycle is about 1000 CE, corresponding to the Kalachakra itself.
3000 BCE. End of the Neolithic. Writing. Bureaucratic age (Rifkin, Hancock). Kali Yuga (3102 BCE). Mayan epoch (3114 BCE).
900-876 BCE. Kalachakra Root Tantra. Suchandra, First King of Shambhala.
800-200 BCE. Axial Age (Jaspers).
c. 402 BCE. Parinirvana of the Buddha according to most modern scholars, plus or minus approx. 20 years. Kali Yuga + 2,700 years (Ursa Major cycle).
1st cent. BCE. Pali Canon written down on palm leaves for the first time.
1st cent. CE. Fourth Buddhist Council.
320-467. Expansion of Nalanda University.
5th-7th cent. Most Mahayana sutras were completed by the fifth century CE. A few were written as late as the seventh century CE.
c. 799. Padmasambhava visits Tibet. Parinirvana + 1,200 years; + 1,200 years = 1999 CE.
1000. Birth of the first terton,Sangyé Lama.
1012. Kalachakra appears in India (some say 966). Birth of the second terton,Drapa Ngönshé. Padmasambhava predicted that the advent of the first tertons would correspond with the advent of the era of the mappo.
1027. Kalachakra introduced to Tibet. Advent of the Kalachakra era (KE).
1197. Sack of Nalanda University by Islamist invaders.
1391-1474. First Dalai Lama.
1578. Third Dalai Lama.
1642. Fifth Dalai Lama. Sovereignty of Tibet established.
1860. Revival of Buddhism in Sri Lanka.
1908. Allan Bennett (Ananda Metteyya) leads the First Buddhist Mission to the West.
1927. Aniruddha (Tib. Magakpa) (1927-2027). Who Draws and Binds the Entire Three Worlds. Aniruddha, the present Kalki king, was prophesied to rule in a time when Vajrayana Buddhism and the Kalachakra are nearly extinguished.
1959. 14th Dalai Lama leaves Tibet, enters India.
1999. Padmasambhava + 1,200 years.
2010. Nalanda International University established on site of original Nalanda University.
2012. 1012 + 1,000 years.
2025. 14th Dalai Lama turns 90.
2027. Narasingha (Tib. Miyi Senge) (2027-2127). Ruling by the Wheel, Holding the Conch. Kalachakra Era + 1,000 years.
2045. Year of the Singularity (Ray Kurzweil).
2064. 2424 – 360 years (one deva year).
2100. Parinirvana + 2,500 years. Kalachakra (900 BCE) + 3,000 years. Buddhist 3,000-year cycle associated with the udumbara, the blue lotus flower, said to bloom once every 3,000 years. The Buddha attained Enlightenment, at the age of 35 under this tree.
2299. End of second Ursa Major cycle from the Kali Yuga and one Ursa Major cycle from Parinirvana.
2327. Raudra Chakrin (Tib. Dakpo Khorlocen). Forceful Wheel Holder. The Kalki king prophesied to appear to humans all over the world in 2424 to defeat the degenerate world rulers, establishing a planetary Golden Age. He is the last king prophesied in the Kalachakra.
2424 CE. Manifestation of Shambhala (i.e., Buddhist global technocratic civilization). Advent of the “Age of Aquarius.” 300 years after 2124. 360 years after 2064. 3,300 years after Kalachakra Root Tantra.
- Various Buddhist schools refer to cycles of different lengths, but upon analysis we discover that all of the cycles are divisions or multiples of the original 5,000 year cycle declared by the Buddha, i.e., 500 years; 1,000 years; 2,500 years; 5,000 years; and 10,000 years (Dane Rudhyar has discussed the significance of the 10,000 year cycle in his book, Astrological Timing: The Transition of the New Age (1969), chapter 2, “Planetary Cycles.”) Thus, all of these cycles are interdependent. The crucial moments appear to correspond to the advent of the Age of Degeneration (Kali Yuga, Mayan epoch, “bureaucratic age,” etc.) about 3000 BCE, the advent of the first Kalki king about 1000 BCE, the advent of Shakyamuni about 500 to 400 BCE, the advent of the Indian Kalachakra about 1000 CE, the Dharma Transmission to the West about 2000 CE, and the manifestation of Shambhala about 2400 CE.
- According to the currently accepted ayanamsa (Wikipedia) of 23.85 degrees (2000), or 24.045 576° (2014), at the current rate of 50.290 966 arc seconds per year (an approximation, since the rate of precession is currently increasing), the Age of Aquarius will commence in 2014 + 426.238 114 years = 2440. This is only 16 years later than 2424. If we accept 2424 as the advent of the Age of Aquarius, the Age of Pisces began in 276 CE, somewhat after the lifetime of Ptolemy (90-168), the great Western astronomer, who stated that the tropical and sidereal zodiacs coincided about his time. 276 CE falls into the second half of the Crisis of the Third Century, when the Roman Empire (Age of Aries) fell into anarchy and effectively ended the era of Roman hegemony, leading to the Triumph of the Church beginning in 313 (Age of Pisces). This implies a current ayanamsa of 24.272 412 degrees. Thus, each astrological age equals 2,147.5 years, an entire “great year” taking 25,770 years to complete, just under the round number estimate of 26,000 years, based on one degree of precession per 72 years. (The average of the three major systems of ayanamasa today [viz., Krishnamurti, Lahiri, and Raman] gives an ayanamsa of 23.55°, which gives a date of 2014 + 461.819193 = 2475. That given above is close to the Lahiri. The current Lahiri ayanamsa of 24.0672 degrees gives a slightly closer year estimate of 2438. The Krishnamurti ayanamsa only differs from the Lahiri by 7 minutes of arc or 8 years of time later. The median value of a list of 22 ayanamsas was 23.904 444 degrees. A simple ayanamsa of 24 degrees projects to 2443.) According to Dr. Alex Berzin, “according to the Kalachakra Laghu Tantra, the invasion will occur 1800 years after the founding of the non-Indic invaders’ religion. If we take that religion to be Islam, which was founded in 622, the date of the Hijra and start of the Muslim calendar, then 2422 is 1800 years after that. However, the Kalachakra Laghu Tantra also states that 403 years before the start of the 60-year prabhava calendar cycle was the year of Muhammed. The first year of the Kalachakra prabhava calendar was 1027, which puts the year of Muhammed and presumably, what the Tantra considers the founding of Islam as 624, which makes 2424 to be 1800 years after that. 624 was the year of the Battle of Badr, the first battle of Islam and marked as the year that Islam began to spread. That would be a fitting event for the Kalachakra Tantra to consider as the start of the invader’s Dharma” (personal email communication, January 30, 2015; quoted with permission). 1,800 is half of 3,600, 60 x 60 and an important number in the Kalachakra (see Berzin, “Kalachakra Does Not Advocate or Predict an Actual World Armageddon“). The 1,800-year cycle implies a 3,600-year cycle, therefore. In fact, 2424 – 3600 = 1177 BCE, which has been called “the year civilization collapsed” (see Eric. H. Cline, 1177 CE: The Year Civilization Collapsed, passim). Similarly, the duration of the Kaliyuga is declared to be 360,000 years (confer 2424 – 360 years = 2064 CE. 360 human years is the length of one deva year.).
- The Kalachakra identified the “barbarian dharma” with what would now be called Islamism, influenced by current events, just as the early Christians identified the Antichrist (= the Kalki Avatar) with Nero. However, this identification may be historically contingent and not necessarily relevant in the future.
Weisstein, Eric (2007). “Precession of the Equinoxes.” World of Physics. http://scienceworld.wolfram.com/physics/PrecessionoftheEquinoxes.html.