B) Rudradaman I in AD 78

Explanation:
The Saka Era, also known as the Shalivahana era, is a historical calendar era that is widely used in India. It is believed to have been started by King Rudradaman I of the Western Satraps in 78 AD.

The Saka Era is based on the lunar calendar and begins with the coronation of King Shalivahana, also known as Gautamiputra Satakarni. However, it is King Rudradaman I who is credited with popularizing and institutionalizing the use of this era.

Rudradaman I was a king of the Western Satraps, who ruled over present-day Gujarat and parts of Maharashtra and Rajasthan in the 2nd century AD. He was a patron of art, literature, and religion and is known for his extensive inscriptions that provide valuable historical and cultural information.

During his reign, Rudradaman I issued a number of inscriptions that mention the Saka Era. These inscriptions were found in various locations, such as Junagadh, Girnar, and Mathura. The inscriptions mention the regnal year of Rudradaman I as well as the Saka year, indicating that he used the Saka Era as an official calendar system.

The Saka Era became widely used in India for dating purposes and continues to be used in various regions of the country. It is used alongside other calendar systems, such as the Vikram Samvat and the Gregorian calendar.

In conclusion, King Rudradaman I of the Western Satraps is credited with starting the Saka Era in 78 AD. His inscriptions and patronage of the era helped popularize its use in India.