Puraan state that it is 1500 years between King Pareekshit and the start of rule of Nand, We know that Pareekshit started his rule in 3102 BCE, just at the end of Dwaapar Yug, and hence, the rule of Nand is dated to 1602 BC. Nand have ruled for 100 years ie till 1502 BC. After this, Nand have ruled for 137 years, with Brihadrath, the last king ruling for 7 years. ie till 1365 BC.

Till here, most of the Puraan agree. It is here that Matsya Puraan gives us some extra information. While Brihadrath was killed by his Shung commander, his descendents ruled for 63 years more (since the Puraan states that it is 70 years inclusive of Brihadrath, so we have taken 63 years, after deducting 7 years of his rule) this will land us in 1302 BC. Matsya Puraan declares that " after this, there is a king Shak who came by and ruled for 26 years" Thus, we can take 1302 BCE to be the first Shak era.

Puraan also declare that Shak ruled for 380 years, means until 922 BC when the Yavan came into the picture. They ruled for 82 years, it means until 840 BC. After this, Tushaar or Kushaan started their reign. While Kushaan ruled for 500 years or so, there are many dynasties such as Mundaa (200 years), Mlecchh (300 years) and Puru (300 years) might have ruled the North-Western parts of India.

The rule of Mlecchh started in 550 BC or so with Cyrus. The rule of Puru came to an end in 327 BC, when Alexander subdued them. After this, there are others who ruled for more than 150 years till Kharavela (Vishwa Sphootika) appeared on the scene in 188 BC or so.

From the inscriptions of Kushaan, Vima Taktoo or Vima Tushaar was ruling around 270 Yavan Era, means 922-270 = 652 BC.

Kushaan belonged to around 1st Century CE? There is not a single irrefutable evidence for this. In fact, there is evidence to the contrary, if at all. The Chinese annals talk of some Chinese tribes who are equated to Kushaan not because they WERE Kushaan but because they belonged to pre determined time frame. But did any one notice that there is no "one to one" relationship between the kings mentioned in these annals and those of Kushaan? In fact, Chinese go on to say that Kushaan (or what we think them to be) did not rule India directly, but placed them under a Commander, which is not at all true in case of Kush. On the other hand, Pauranik chronology fits greatly with the time frame of Kushaan.

It is Kushaan who spread the iconography of Indian gods, probably combined with Buddhism in Bactria and Iran. Vima Taktoo ruled around 650 BC (922 BC -270 = 652 BC). That spread of Buddhism in Iran is pre Zoraster has been amply documented by Al Beruni. That Kushaan are prior to Zoraster is amply proved by the fact that Ahur Mazda was not given a prime place in the Iranian pantheon of deities struck on Kushaan coins. Later Kushaan were perhaps made to restrain themselves, to Gaandhaar in specific, during early 5th century and this gap gave a chance for cultural upheavals to rise against these Indian elements in Persia.

Consequently, a religious revolution was brought about by Zoraster perhaps in early 5th century who has brought Ahura Mazda into the forefront of the Iranian deities, probably in accordance with early Persian Texts. He was followed by Xerxes I of Persia (r. 485 – 465 BC) who proudly proclaimed over his destruction of Daiv:

"Among these countries (that submitted to him) was (one) where previously Dev were worshipped. Then, by the favor of Ahura Mazda, I destroyed that Dev place, and I had proclaimed, the Dev shall not be worshipped. Where previously the Dev were worshipped, there I worshipped Ahura Mazda properly with the Law (arta)." There is no doubt in identifying these Dev as Indo Aryan Gods.

There is another support for our hypothesis. If Yavan era started in 922 BC, Avaca kings have to be ruling Swat area sometime around 700 BC. The numismatic sequence shows that the Avaca kings  followed by one Sasa or Sasi, who is not otherwise identified. However, we know that the kingdom of Aswikas was destroyed by Alexander who has imposed Sasi Gupta on the Aswika people. Thus, the Sasa of these coins is none other than the commander of Alexander, who perhaps declared independence in post Alexandrian times.
[From India Handbook, 1996]