From this old post we get a list of why we shouldn't take those fanatics seriously:
What do they all (the apocalypses) have in common? Several things.
1. They all required immense, immediate governmental action,
2. action favored by leftists,
3. action that would have a seriously adverse effect on the global economy and prosperity,
4. to forestall apocalyptic consequences.
5. None of them happened.
Here's some more information to consider, go take a read.