The Bikrami calendar, also called Vikrami calendar or sometimes Hindu calendar,
 is named after king
The Vikrami era ancient calendar has been historically used by
The Vikrami calendar is similar in conceptual design to the Jewish calendar, but different from the Gregorian calendar.
 Unlike Gregorian calendar which adds additional days to lunar month to adjust for the mismatch between twelve lunar cycles (354 lunar days)
 and nearly 365 solar days, the Vikrami and Jewish calendars maintain the integrity of the lunar month, but insert an extra full month by complex rules, every few years, to ensure that the festivals and crop related rituals fall in the appropriate season. This Indian system of calendar keeping is one of the luni-solar calendar systems innovated in ancient human cultures.
 Early Buddhist communities of India adopted the ancient Indian calendar, later Vikrami calendar and then local
The Vikrami samvat (Bikrami Samvat system) has been in use in the Indian subcontinent since ancient times, and remains in use by the
The Vikrami era, or Vikrami-samvat, is notable because many historic manuscripts and inscriptions use it. However, in early inscriptions such as the Badva yupa inscriptions and Mandasor inscriptions, the term Vikrami-samvat is not used, rather the same calendaring system is found by other names such as Krta (Krita) and Malava. 
In the colonial era scholarship, Vikrama-samvat was believed to be based on the commemoration of King Vikramaditya expelling the Sakas from Ujjain. However, later epigraphical evidence and scholarship suggests that this theory has no historical basis and very likely was an error. Until the 9th century, the same era is inscribed in numerous archeological sites by other names such as Krta and Malava. Starting in the 9th century and thereafter, epigraphical artwork uses Vikrama-samvat, suggesting that sometime around the 9th-century, the Hindu calendar that was already in use became popular as Vikrami calendar, while Buddhist and Jain epigraphy continued to use an era based on the Buddha or the Mahavira.