As there are seasonal changes within a year, so there are changing ages in the duration of the manifest cosmic world. These changing ages are called  yugas , or periods. As there are three modes of nature, there are also various ages dominated by these three modes. The period dominated by the mode of goodness is called Satya-yuga, the period of passion is called Tretā-yuga, the period of mixed passion and ignorance is called Dvā-para-yuga, and the period of darkness and ignorance (the last period) is called Kali-yuga, or the Age of Quarrel. The word  kali  means “quarrel.” Kali-yuga is compared to the rainy season because many difficulties in life are experienced during this damp season.
In Kali-yuga there is a dearth of proper guidance. One may take guidance in the evening from the stars and moon, but in the rainy season the light of guidance comes from insignificant glow-worms. The real light in life is the Vedic knowledge. The  Bhagavad-gītā  affirms that the purpose of the  Vedas  is to know the all-powerful Personality of Godhead.
sarvasya cāham hṛdi sanniviṣṭho mattaḥ smṛtir jñānam apohanaṁ ca vedaiś ca sarvair aham eva vedyo vedānta-kṛd veda-vid eva cāham
“I am seated in everyone’s heart, and from Me come remembrance, knowledge and forgetfulness. By all the Vedas am I to be known; indeed I am the compiler of Vedānta, and I am the knower of the Vedas.” (Bg. 15.15)
16