They even gave her the date: May 13, 2003.
Friends of Nancy took her story and turned it into a hoax to scare gullible people. The charlatans made money by selling books (the the scared people) on how to survive.
After May 2003, they wanted to run the hoax again, so they picked a new date (using José's lie) and "improved" the hoax by adding lots of other lies (many coming from older hoaxes).
There are NO signs that December 21 is the end of time because the whole thing is a lie.
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Global warming is real. It has nothing to do with 2012 (it is a process that happens over very long periods. Global warming is easy to prove (measure the extent of glaciers all over the workd, for example).
What is more difficult to determine is whether human activity has any effect on Global warming. Since both "sides" on the debate have invested lots of money on their views, we will never know the truth. For example, the coal industry in the USA means trillions of dollars. Do you thing they even want us to think about Global warming? Of course not.
Other companies have invested gazillion dollars developing products that pretend to slow our impact on Glabal warming (for example, the new 5 dollar light-bulbs); do you think these companies want to find out that Global Warming is not caused by humans? Of course not.
The only thing we know for sure is that Global Warming is happening and that it has nothing to do with 2012.