The viewpoint of most of those who take a futurist approach to Revelation is that the antichrist will be in power for 42 months or 1,260 days. This is based on the reference to “times, time, and a half a time” which is taken to refer to a period of three and a half years.
An image that I saw on Facebook, but unfortunately now can’t seem to track down, pointed out that Barack Obama has successfully passed that number of days in office, and is thus owed an apology from those who said he was the antichrist.
The sheer number of people who made such claims is disturbing, and so they can now choose to admit either that they were wrong, or the Bible is wrong, or they were wrong in their understanding of the Bible. For them to admit that they were wrong about anything, given their dogmatism and confidence, would be an enormous achievement.