The designation of a calendar year as belonging to a particular era, and so its assignation to a particular date, has varied widely on the subcontinent, depending upon geographical region and local history. Among the better known conventions are the Śaka era (1= 77/78 ce), used for the Indian National Calendar, and the vikrama era (1= 57/58 bce). ‘Saṃvat’ indicates ‘in the year … of the vikrama era’. ce (Christian or Common Era) is widely used for secular purposes. For the mythological conceptions of eras, see cosmogony; yuga.