^That is absolutely correct GG.
However, if someone in the mid U.S. were to post an 8 hour emergency at 10 pm, this would mean the deadline is 6 am their time. However, since the majority of U.S. members probably go offline/to bed around this time, it would mean there would be VERY few replies from members in that country. However, for members of Singapore (which I believe is 6 hours ahead), this would mean an 8 hour time span for them is 4 am - 12 pm that your message would show up and you may get some replies from people in that time zone. Does that make sense?
So basically each member would have to look at the time stamp on the message (which should show up in their local time), and estimate the amount of hours from the time of posting to see what time is left. This is one of the reasons why the posts would have to be locked at the end of the time to help keep confusion down.
But, I definitely see all of the negatives of this idea as well, which people have brought up. I dunno, it was just a thought but maybe wouldn't work the best.