Kālidāsa
The most popular theory is that Kalidasa flourished during the reign of Chandragupta II, and therefore lived around 4th-5th century CE. Several Western scholars have supported this theory, since the days of William Jones and A. B. Keith. Many Indian scholars, such as Vasudev Vishnu Mirashi and Ram Gupta, also place Kalidasa in this period. According to this theory, his career might have extended to the reign of Kumaragupta I (r. 414 – 455 CE), and possibly, to that of Skandagupta (r. 455 – 467 CE).
Kali Yuga
According to the "Surya Siddhanta", Kali Yuga began at midnight (00:00) on 18 February 3102 BCE. 
This is also considered the date on which Lord Krishna left the earth to return to Vaikuntha. This information is placed at the temple of Bhalka, the place of this incident (see photo). 
According to the astronomer and mathematician Aryabhatta the Kali Yuga started in 3102 BCE. He finished his book "Aryabhattiya" in 499 CE, in which he gives the exact year of the beginning of Kali Yuga. He writes that he wrote the book in the "year 3600 of the Kali Age" at the age of 23. As it was the 3600th year of the Kali Age when he was 23 years old, and given that Aryabhatta was born in 476 CE, the beginning of the Kali Yuga would come to (3600 - (476 + 23) + 1 (As only one year elapses between 1 BCE and 1 CE) = ) 3102 BCE.