A Very Happy New Year to All of You.
Meg has pointed to a very interesting point. There are calendars and calendars. In my country of 1200 million people and at least 20 large linguistic and ethnic groups, there can be a new calendar starting every month for a section of people. Olden days, every major King or Emperor would start a new calendar that started with his reign. Thankfully, the Gregorian calendar is common to all now.
Regards
SNM