Within Hindu scriptures, cycles of time are measured in yugas, of which there are four – the Satya Yuga, Treta Yuga, Dvapara Yuga, and Kali Yuga. Some schools of Buddhism, particularly Tibetan Buddhism, also teach the yugas, as do other religions such as Sikhism. By most interpretations of the ancient scripture, we are currently in the final stage, or Kali Yuga, before the cycles begin again with the Satya Yuga.
Yugas are many thousands of years long, and are not just related to earthly existence. The most common belief among scriptural scholars is that the current Kali Yuga began around 3100 B.C. and will continue for 432,000 years. However, there are notable dissenters to this view, including Sri Yukteswar, best known as the teacher of Swami Yogananda, founder of the Self-Realization Fellowship, who believed the dates had been miscalculated, and that we are actually in the Dvapara Yuga.
The Kali Yuga is named after the Hindu demon Kali, which is not the same as the goddess Kali, as is sometimes assumed. The nature of the Kali Yuga is degeneration, discord, and strife. It is characterized by the breakdown of systems and structures, including family, social, political and religious or spiritual structures. It is sometimes called the 'dark age' – a time in which teachings of enlightenment are harder to access and truly live. The tribal or possessive aspects of the ego are highlighted during this time, resulting in constant discord and strife, with each political, social, or religious group certain their agenda is paramount.
Because of these themes, in modern times theories of the Kali Yuga are often compared to Christian 'end days' predictions, or Mayan calendar 2012 theories. Yugas are quite different though, in that they are clearly cyclical – each yuga plants the necessary seeds for the succeeding one. Teachings on the Kali Yuga also emphasize that although it is a dark time, it is also an accelerated one, and thus the potential for spiritual advancement, and particularly for enlightenment, is actually very great, for those interested.
Particularly in Vajrayana or Tantric Buddhist lineages, which utilize esoteric energy practices and guru/deity meditation to achieve awakening in one lifetime, many teachers emphasize that this period is an especially good time to practice the dharma, or Buddhist teachings.
Jetsunma Ahkon Lhamo, an American women recognized as a reincarnated lineage holder within the Nyingma school of Tibetan Buddhism, describes it in this way in her essay Vajrayana and the Kali Yuga:
"This time of Kaliyuga is extremely contracted. Karma is thick. It isn't spread out and dispersed over a great, long field. Rather, it is drawn in. It is a time of contraction, and karma ripens much more quickly than it used to ripen...Under these conditions, Vajrayana can actually do the most good...we can see cause and effect relationships more readily. We are suffering and we are suffering just enough to help us be convinced that suffering is a reality, therefore we are willing to practice. We realize the benefit of practice because we truly do wish to attain enlightenment."
Pabongka Rimpoche, of the Gelug school, notes that:
"Most important of all through this physical rebirth you are able to achieve the state of Vajradhara [unification of the illusory body and great bliss] within one short lifetime in this degenerate age; otherwise it would take thee countless great aeons to achieve. Thus this rebirth is worth more than one thousand billion precious jewels."
Some contemporary Buddhist teachers see signs of the coming Satya Yuga in the growing interest in spirituality outside of formal religion. Others feel that a lot more deconstruction of existing social and worldly structures will occur first. Many branches of Buddhism do not concern themselves at all with cycles of time, teaching that the fundamental nature of existence, as the Buddha outlined in the Four Noble Truths, is the same in any age.