When people look back on the period of 2011 and 2012, they may remember it as a time when the world was supposed to end.
That's assuming, of course, that the world doesn't actually end.
Fact is, these times are rife with doomsday predictions, be it Harold Camping's failed end-times prediction this past May to his updated doomsday date of Oct. 21.
You may prefer to fret about Dec. 21, 2012, when the Mayan calendar runs out, and then there are those dubious rumors that Comet Elenin could hit Earth as early as Sept. 11.
Even though world is as likely to end on these dates as it was on previous end-of-the-world dates (meaning it won't), there is no reason not to prepare for the worst, right?
That's the thinking of "John," a business consultant in Colorado, who has spent the last five years building a doomsday shelter just in case there is a calamity of biblical proportions.
"I first started decided to build one in 2006 because of the economic climate," said John, who asked that his location and last name not be revealed, in case the worst happens and people show up at his home trying to get inside.
"I could see there were a lot of rogue groups, and I knew there was a housing bubble as early as 2004. I would drive down the road and see all these houses and wonder where all the money was coming from."
Since then, other potential threats -- including wacky weather, Japanese earthquakes, the Mayan calendar, the alleged arrival of a "Death Star" called "Planet X" that is supposed to wreak havoc here as well -- have made him feel secure that he made the right decision.
"We've gotten out of real estate and converted everything to gold and silver," he said.
Oh, and there's that doomsday shelter.
"To be honest, we consider it more of a safe room," John said. "My builder, Joe Campo, dug next to the home and created a tunnel that leads to the shelter. He covered it in dirt and basically extended our home."
The shelter, which cost around $300,000, is big enough to keep John's wife and two kids safe and snug from nuclear war, tornadoes and, hopefully, telemarketers for up to 30 days.
"We stocked it with food," he said. "But we rotate it. If you're going to spend 30 days inside, you better have food you like."WATCH:
Not only does the home have state-of-the-art filtration systems for air and water, but John says Campo "saw into the future" and installed filters to protect against electromagnetic frequencies.
According to Campo, who is also currently racing to build several of state-of-the-art floating Noah's Ark-style survival shelters by 2012 on 80 acres of property in Alamosa County, Colorado, EMFs are the unsung doomsday danger.
"This is a very serious issue. NASA has recently published information warning the people that they forecast severe solar storms for 2012 and 2013," Campo said by email. "It shows a strange scenario of a gigantic solar storm or solar flare breaching our magnetic sphere, torching a satellite. It appears to be prophetic in nature and is open to interpretation."
Although John takes pride in his doomsday shelter, he doesn't use it for entertaining and doesn't let anyone know about its existence.
"I don't use it for entertaining," he said. "My parents are the only ones who know -- that's it."
That includes building inspectors, John admits, although he quickly adds that everything his builder did exceeded any code or regulations because it's designed to survive practically every type of conceivable disaster.
Campo declined to discuss John's comments, citing a confidentiality agreement he signs with every client, but he is convinced that he is doing his best to help those who want to be prepared just in case something dreadful happens.
"No one responsible is saying that it is the end of the world, but there is alarming evidence that most of us may be living on borrowed time," Campo said. "Clearly the recent Japanese tsunami, earthquake and nuclear meltdown was merely the tip of the iceberg."
Campo learned much of his skills building doomsday shelters by building 1,500 McDonald's restaurants.
"There are some similarities," he said. "McDonald's had three or four different plans, but they ended up looking the same. But many of those had underground areas that were sort of like minishelters, with emergency generators, but the walls weren't as thick."
Campo got interested in the doomsday market after 9/11, but has seen interest skyrocket in recent years because of the aforementioned Mayan prophecies and other alleged end-of-world predictions.
Despite his suggestion that "there is alarming evidence that most of us may be living on borrowed time," he insists that he is not fear-mongering to get business.
"I do not believe the world is coming to an end, and I refuse to use fear tactics," he said.
Campo also points out to potential customers that even if the shelter isn't needed for survival, it can also work as a basement or spare room.
"This is not like an austere post-World War II-type shelter," he insisted.
Although some people have doomsday shelters built for them, others prefer to do the work themselves, such as "Glenn," a liquidator in east Texas, who has built a shelter using a kit purchased from Monolithic, an Italy, Texas-based maker of dome-home kits. Glenn is a survivalist who decided to build the underground home inside a mountain near his house.
"In the long term, things are not going to be as they are now, and I might need the extra benefit," he said.
It doesn't have to be a flood or a tornado or an earthquake, he said, even the record heat plaguing much of the country is reason enough.
"It's got a great insulation factor," he said. "We are protected from hurricanes, tornadoes, bullets and bombs. And the utility bills are low."
There is one thing that the home may not be safe from (two, if you count the aforementioned telemarketers).
"The only thing that could be a problem is a flood, but I am higher than my neighbor's house."
Another issue: The homes are dark when the power is out, which Glenn says means he has to keep flashlights and candles on hand.
"There's an upside to that, though," he laughed. "You don't have the sun shining in your eyes in the morning."
David South is the CEO and President of Monolithic Dome Institute, the company that supplied the dome-home kit to Glenn. It has been in the business for 35 years.
Depending on what is happening, his product appeals to different groups.
"Sometimes people buy them to store potatoes or for underground homes, and I've been getting calls from Joplin, Mo., from people trying to rebuild after the tornado."
Although many people want to build them underground, South says that's not really necessary.
"The basic egg shape is the strongest there is, and with concrete it becomes stronger," he said. "My buildings can handle pretty much anything."
South says his dome homes cost the same as any custom home, but recommends that any person who wants one should write down what they want the home to do.
"Do you want it to protect you? Well, who or what do you want protection from? What do you expect it to do?" he asked rhetorically. "If you're worried most about nuclear fallout, you'll have to bury it five feet underground. On the other hand, if you fear tornadoes, put it on top of your property because those really only happen once every 40 years."
South has a droll, laid-back way of speaking that probably comes, in part, from surviving 35 years of doomsday predictions. Although he seems comfortable that the end of the world is probably not nigh, he says it never hurts to have a plan.
"If we live long enough, we learn that we don't know what will happen tomorrow," he said.