^ this
The calendar had to end at some point.
Sure, human have invented the calender.
The calender has nothing to do with such a things.
We just using it to indicate data.
Human does not live long on earth yet either.
If the world would exist 24 hours, human are there for 15 seconds at this moment.
Things that happened in the past (they think that happend), could happen again, sure.
Like a huge meteorite hits earth, or a supervulcan that erupts.
Just happen very rarely.
The universe is just massive, and so it earth.
Nature rules and does his thing.
The only thing that is strange is like some people call God.
There are lots of common things in different ages, and calling them different names and such.
Maybe aliens are those Gods, and helped us, did things at earth.
How strange are the equal buildings in Egypt and other civilizations?
Check Ancient Aliens at Youtube. Amazing theory's there.
That are documentary's from Discovery I guess, not a amateur thing.