How are the muslim and chinese calendars different

If Christ saved everyone in the whole world, why haven't the whole world adopted to his calendar?

I think the Chinese have 8,400 years on their calendar.

And Jewish have 7,210 years on their calendar.

How can they have more years, if the world is only 6,000 years old?

Ithink a. cause egyptians worship a status and i havent even heard of c in my life.

Word of mouth.