I've proposed dates and times for the convention. They are listed at the Schedule page.
20, 21 February 2010 is a weekend that seems to be without a major conflict in all the countries I could check.
Three sessions, each session is 6 hours long, and there is a 3 hour break between the sessions. This covers a 24 hour period with most major regions in the world having 1 session during the day, 1 in the evening, and 1 in the middle of the local night. This means that any presenter should be able to find a slot during their prefered times.