This is the central part of the home page of www.familyradio.com, as it appears today (21 May 2011). According to Harold Camping, today is Judgment Day, the Second Coming of Christ and the Rapture. Wikipedia has an article about his prediction.
In order for as many people as possible to be aware of the approaching Judgment Day, Harold initiated a massive international publicity campaign. “Presently there are over 2000 billboards, posters, and bus posters throughout the world, with many going up weekly.”  Here are some examples of the billboards and buses which people have seen.
So what exactly was meant to happen to the Earth today? Harold was interviewed by the New York Magazine a few days ago:
When we get to May 21 on the calendar in any city or country in the world, and the clock says about — this is based on other verses in the Bible — when the clock says about 6 p.m., there’s going to be this tremendous earthquake that’s going to make the last earthquake in Japan seem like nothing in comparison. And the whole world will be alerted that Judgment Day has begun.
And then it will follow the sun around for 24 hours. As each area of the world gets to that point of 6 p.m. on May 21, then it will happen there, and until it happens, the rest of the world will be standing far off and witnessing the horrible thing that is happening.
What was meant to happen to humanity? From the Family Radio website:
We have already learned that the time of the second coming of Jesus must coincide with the time of the rapture, which in turn coincides with the first day of the 153 days of the day of judgment. That date is May 21, 2011.
On that day, the graves will be opened, and all the dead bodies of those who previously had become saved will be resurrected as glorified spiritual bodies. At the same time, the carcasses, bones, etc., of all the unsaved who had previously died will be thrown out of the graves as filth on the ground.
Those who are still living and are true believers will be instantly changed into their heavenly bodies, and will be caught up to heaven in the sight of all those who are left behind. Indeed, about 6.5 billion people who are left behind will also know that Jesus has come. And we can be very certain that it is at the time of the rapture that everyone will see Jesus in His second coming.
How many people were to have been saved today? “We learn from the Bible that Holy God plans to rescue about 200 million people (that is about 3% of today’s population).” 
I find it amazing to observe the absolute certainty with which Harold spoke about his predictions. From the New York Magazine:
God has given sooo much information in the Bible about this, and so many proofs, and so many signs, that we know it is absolutely going to happen without any question at all.
And from the Family Radio website:
For one to object to May 21st, 2011 one must have BIBLICAL AUTHORITY to do so. Objections cannot be based upon consensus, traditions or fear. God has given far too many biblical proofs for anyone to disregard May 21 simply because he or she does not like it.
This date is not the product of the mind of one man or a group of men. It is no longer opinion, but a matter of fact. May 21, 2011 is God’s date. All other predictions are man’s attempt to predict the end.
Harold is not the first person to have predicted the date of Judgment Day, nor will he probably be the last. Wikipedia contains a list of predicted dates of the end of the world, and also comments on this phenomenon of “date setting”:
Over the last few centuries, believers in the rapture of the church have made predictions regarding the date of the event.
Any individual or religious group that has dogmatically predicted the day of the rapture, referred to as “date setting”, has been thoroughly embarrassed and discredited, as the predicted date of fulfillment came and went without event.
Some of these individuals and groups have offered excuses and “corrected” target dates, while others have simply released a reinterpretation of the meaning of the scripture to fit their current predicament, and then explained that although the prediction appeared to have not come true, in reality it had been completely accurate and fulfilled, albeit in a different way than many had expected.
Slate.com published a great article yesterday called “Prophecy Fail: What happens to a doomsday cult when the world doesn’t end?”, and it’s well worth reading. Here are a few extracts:
We’ve yet to learn what motivates people like him to predict (and predict again) the end of the world, but there’s a long and unexpected psychological literature on how the faithful make sense of missed appointments with the apocalypse.
The most famous study into doomsday mix-ups was published in a 1956 book by renowned psychologist Leon Festinger and his colleagues called “When Prophecy Fails”.
Festinger was fascinated by how we deal with information that fails to match up to our beliefs, and suspected that we are strongly motivated to resolve the conflict—a state of mind he called “cognitive dissonance.”
… it’s easy enough for a believer to reinterpret and revise the details of a prediction so that it fits whatever facts are on the ground. The research literature is littered with such examples.
… it is easy to write off the believers as deluded, but Festinger was not so wide of the mark when he suggested that we adapt to even the most unlikely of contradictions using nothing more than our methods of everyday rationalization.
I’ll be very interested to see whether Harold announces any kind of explanation for the failure of his predictions …
Photo of Harold Camping used under Creative Commons license.