Vikram Samvat (IAST: Vikrama Samvat; abbreviated VS) or Bikram Sambat B.S. and also known as the Vikrami calendar, is a Hindu calendar historically used in Nepal. Vikram Samvat is generally 57 years ahead of Gregorian Calendar, except during January to April, when it is ahead by 56 years. Alongside Nepal Sambat, it is one of the two official calendars used in Nepal. In India, it is used in several states. The traditional Vikram Samvat calendar, as used in India, uses lunar months and solar sidereal years. The Nepali Bikram Sambat, introduced in 1901, also uses a solar sidereal year. A number of ancient and medieval inscriptions used the Vikram Samvat. Although it was reportedly named after the legendary king Vikramaditya, the term "Vikrama Samvat" does not appear in the historical record before the 9th century; the same calendar system is found with other names, such as Krita and Malava. In colonial scholarship, the era was believed to be based on the commemoration of King Vikramaditya expelling the Sakas from Ujjain. However, later epigraphical evidence and scholarship suggest that this theory has no historical basis. During the 9th century, epigraphical artwork began using Vikram Samvat (suggesting that the Hindu calendar era in use became popular as Vikram Samvat); Buddhist and Jain epigraphy continued to use an era based on the Buddha or the Mahavira. According to popular tradition, King Vikramaditya of Ujjain established the Vikrama Samvat era after defeating the Śakas. Kalakacharya Kathanaka (An account of the monk Kalakacharya), by the Jain sage Mahesarasuri, gives the following account: Gandharvasena, the then-powerful king of Ujjain, abducted a nun called Sarasvati, who was the sister of the monk. The enraged monk sought the help of the Śaka ruler King Sahi in Sistan. Despite heavy odds but aided by miracles, the Śaka king defeated Gandharvasena and made him a captive. Sarasvati was repatriated, although Gandharvasena himself was forgiven. The defeated king retired to the forest, where he was killed by a tiger.