And the ten horns which thou sawest are ten kings, which have received no kingdom as yet; but receive power as kings one hour with the beast.
Be interesting to know how long this hour is. I have seen people claim that they did the math on this and came up with three and a half years , but I personally don't know as I never bothered to chase it up.
Revelation 12:6 speaks of one thousand two hundred and sixty days of "the woman" being protected in the wilderness from the dragon. I think the woman is the numbered (144,000) Jewish believers in Jesus who are protected with the special seal (Revelation 7:1-8, also Revelatiom 14:1-). It also says she flees from the serpent and is nourished in the desert for a time, times, and a half a time (Revelation 12:14). Because the dragon is unable to kill these, he turns his attention to the rest of the believers, who I believe refer to Gentile and un-sealed Jewish believers in Jesus. (This seal in Revelation 7, 14 is not the Holy Spirit, but it protects them from being killed by the plagues that come on the earth.)
One thousand two hundred and sixty days is roughly three and a half years, and by context it appears that "a time, times and a half a time" apply to this same period of protection to the Jewish sealed believers in Jesus.
Also, Revelation 13:5 says the beast of the sea was given authority to speak blasphemies for 42 months. This is also 3.5 years. 12 + 12 + 12 + 6 = 42
And Daniel 9, speaking of seventy sevens (shown to be of seven years each by the reference to Messiah at the end of the 69th week) suggests that in the middle of the last seven (Daniel 9:27), there will be the stopping of sacrifice and the abomination that causes desolation. (Halfway through seven years is 3.5 years.) Daniel 11:31 attributes these things to an evil person, not to Jesus (there is some debate about the "he" of Daniel 9:27 but I believe when you compare it with Daniel 11:31, it's obviously talking about an evil person--an Antichrist.)
Daniel 12:7
7 Then I heard the man clothed in linen, who was above the waters of the river, when he held up his right hand and his left hand to heaven, and swore by Him who lives forever, that it shall be for a time, times, and half a time; and when the power of the holy people has been completely shattered, all these things shall be finished.
Daniel 12:11 says from the time of the daily sacrifice being removed and the abomination that causes desolation, there will be 1,290 days (again, about 3.5 years). And it says blessed are those who wait 1,335 days.