sentences:  The Gregorian calendar is the official calendar of the Republic of Indonesia and civil society, while the Islamic calendar is used by Muslims and the Indonesian government for religious worship and deciding relevant Islamic holidays.The Javanese calendar is used by the main ethnicities of Java island—that is, the Javanese, Madurese, and Sundanese people—primarily as a cultural icon and identifier, and as a maintained tradition of antiquity.The Javanese calendar is used for cultural and spiritual purposes.