The calendar we use is called Gregory Calendar after the Pope. Just in recent times Turkey has switched to the Catholic calendar but many in Turkey want to go back to their Muslim roots,
Recent attack in Turkey New Years day was against the Calendar. People in Pakistan protest against celebrating New Years day. In another 50 years they could all go back to their calendar (Muslim ) With computers with could have all calendars on the menu box (Catholic, Moslem, Julian, Hindu etc)