No set dates for most of these yet:
Week 1 - Friday Aug 14 - at Seattle - 8:00 pm MT
Week 2 - Saturday Aug 22 - at Houston - 6:00 pm MT
Week 3 - Saturday Aug 29 - vs SF - 7:00 pm MT
Week 4 - Thursday Sept 3 - vs Arizona - 7:00 pm MT
The complete preseason schedule for all times, if you're interested:
http://www.nfl.com/news/story/0ap300...eason-schedule
Edit: official dates and times announced - post updated.