I will be receiving calls from folks over the next couple days or seeing crap on Facebook. The key to pulling this off will involve being 100% serious and believing it yourself.
Plan - Make a big big deal over the new light that the end will occur in this Millenium, and immediately point out that this is huge news as a date hasn't been pushed since 1975.
Why - first off you use this as a way to bring in 1975 and tarnish the AGM with that debacle. But, you have to do it excitedly and with a smile to fake it. You can't come across negative. You must be seen as excited and amazed they used a new date.
Crucial - NEVER address the fact that the date could be 900 years in the future. Play it up and milk it huge. When someone then says to you that the date could be 900 years away act shocked and say they are wrong. Make them prove to you a Millenium is 1000 years. Then act very sad and down. They just used their own minds to push the end off into the very distant future.
What you are doing is pretending you think the end will be here in less than ten years. You've mistakenly thought millenium is Decade. Make them show you how mistaken you are and that he meant sometime in next 900 yrs.