Someone emailed me about my previous response to the Two Witnesses to let me know it seemed too terse to them and deserved a more respectful answer.

I apologize if that was other's impression as well. One can come across that way when pressed for time and trying to at least help by directing them to something you already wrote touching on the subject. So here's a kinder gentler response:

Here's how we find out how long the Great Tribulation is:

Daniel 9:27 says there will be a league for 7 years and halfway through the sacrifices will be stopped and an abomination erected on a wing of the temple (same day apparently) by the Prince who shall come. (AC)
Dan 12:11 confirms that the sacrifices will be stopped and abomination set up on the same day, adding the detail that its exactly 1290 days from the end of the 7 years, which indeed is in the middle (not to the very day of course).
In Mat 24:15, Jesus says that the abomination spoken of by Daniel immediately precedes the Great Tribulation (the same time of distress during the final End Times King of the North's terrible reign over the whole earth that Dan 11-12:1 speaks about).
Therefore the Great Tribulation must be less than 1290 days long and thus cannot be 7 years long since it starts after the Abomination which is said to come in the middle of the 7 years. This makes it at most 3½ years.

The 1260 days of the Two Witnesses preaching is the same 42 months that the Temple Mount is trampled (Rev 11:1-3) and the same 3½ years that the Woman is protected in the desert (Rev 12:14) which all fit the Tribulation period well and make perfect sense placed there.(How 1260 days = 42 months = 3½ years literally is quite amazing to understand. See this article for that explanation of how it will work:

http://timmchyde.com/revelation-calendar-360-30-day-month-coming.htm )

The reason why the the witnesses do not preach for 1290 days but only 1260 and the gentiles trample for only 42 not 43 months, etc. is because it seems that since the Abomination was given as the only sign by the Messiah of how to recognize when to flee Judea to the mountainous safe place prepared (Mat 24:15-16=Rev 12:14), that there should be time to effectively flee as he commanded. It seems that the Tribulation is only 1260 days and starts 30 days after the sacrifices are setup and the statue of the Beast that the False Prophet commands to be made is set up which is what the Abomination is in case you are wondering (idols are one of only five abominations identified in the Torah and also what Antichus Epiphanes did to the temple with a statue of Zeus in the Maccabees time as a type of the Antichrist),

I hope this answer was better and let me know if someone after reading this still believes the tribulation is 7 years long and why (I'm very curious to know why that idea is so persistent).

Tim