Only the Jehovah's Witnesses and a few extremist Fundamentalist Christian groups believe in an "event" known as "the Great Tribulation." None of the Catholics, Orthodox, or other mainstream Protestant religions have such a doctrine nor interpret Revelation in any manner allowing for such a theological timeline to be considered dogma. Neither Jews nor Muslims nor any other faith have such an expectation either, since these other religions do not view the book of Revelation as inspired. (So the "much speculation" can only be limited to the few people obsessed with the "power" such "special insight" seems to give them before others who fall for such an uneducated view in the first place.)
As the Common English Bible (recently released, and translated by 115 leading biblical scholars from 22 denominations--Catholic and Protestant--demonstrates even in the rendering of the oft-cited and "favored" text of JWs, Revelation 7:13, 14:
One of the elders said to me, "Who are these people wearing white robes, and where did they come from?"
I said to him, "Sir, you know."
Then he said to me, "These people have come out of great hardship. They have washed their robes and made them white in the Lamb's blood."
The word "tribulation" as rendered in the New World Translation may have been "modern" and "up-to-date" with American English when it was released in 1950, but it is not a commonly used word anymore in 2012. We don't say things like: "I am in great tribulation" or even use it to describe anything much at all. The word the average person uses instead in the 21st century is "hardship," i.e., "My family has had to endure great hardship due to the recent financial collapse."
While not dismissing the belief that Revelation does have glimpses of the future in it, the majority of Christians accept the book as "apocalyptic literature," a genre common in and out of Judaism. There are many ancient examples even from heathen sources of this writing technique, and it often used "key phrases" and symbols common in the "lingo" of the group to tell how a current situation would turn out for the better according to the religion's dogma regarding the future.
In Christianity, the book of Revelation is seen as a series of symbolic visions, each describing the then-current persecution of the Christians by the Jewish and Roman communities (with secular Rome as "Babylon the Great"). The "tribulation" or "hardship" the Christians come through was not seen as a singular event in the future, but the ongoing persecution that usually ended in the martyrdom of the Christian faithful. Both the 144,00 and the "great crowd that no one could number" are seen as two different sides of the same scene, each scene beginning with noting the nationality of groups and counting them, and ending with a heavenly reward before God's throne. It should be of interest that the "numbering" of the 144,00 and the assembling of the great crowd do not occur "before" or "simultaneously" with the end of the world, but their completion are seen as the final event in history itself (at least as far as Christians were then concerned). How so? The symbolic vision ends with the "seventh" or final "seal" on God's revelation being opened and followed by "silence," meaning there is no more of salvation history to convey--no 1,000 year reign, nor Armageddon, nothing like the Witnesses detail. Christians see this as a vision describing how members of the Church would never be without having to face opposition and even death from their foundation to the end of the world, but outside of this general display no particular future event is actually described.
One final way to show that the doctrine of "the Great Tribulation" is just another one of those doctrines created because religionists are relying on an old, outdated rendering of words into English, you yourself point of that the same Greek word occurs in Revelation 2:22. Here Jesus is "about" or as modern-renderings show, Jesus is in the act of "throwing her [a group or heretics] onto a sickbed. I am casting those who have committed adultery with her into terrible hardship--if they don't change their hearts from following her practices."--Common English Bible.
Even the Witnesses admit that this was a description of an event occurring in the first century. It could not have reference to a future "Tribulation" event destined to come on the earth, because Jesus said he would keep the "hardship" or "tribulation (NWT)" from happening at all if people repented.
Did you notice how the old-fashioned, out-of-date, and now archaic rendering of "great tribulation" from the NWT, translated more than half a century ago, just means "great" or "terrible hardship." See? The Watchtower has now become guilty of what it used to claim about other religions, using an out-of-date translation and then coming to incorrect conclusions because of not being able to or wanting to see past a certain type of phraseology.
If you're going to be religious, at least throw away your old Bible and get one where you know the education of all those involved in the rendition, and that it has been made fairly due to a balance of religious views. At least crack open a reliable Bible commentary from a well-accepted and credited academic body, like the Oxford editions (or other like publishers). At least put some reason and intelligence behind what you believe--even the atheist who will still disagree with your convictions will have better respect for you (and gosh! you'll treat them better yourself)--because it won't hurt anyone to at least see with full eyes open what the past 2000 years of scholarship has come up with regarding religion, Bible translation, and the like. If your brain doesn't have something worthwhile to process, why would you want your heart to get involved as well?