Fatal error: Class 'DateTimeZone' not found in /home/apang/work/piwik/dev/trunk/core/Date.php on line 207
Note: I have some more testing to do and may expand on this ticket...
Hmm... the DateTime and DateTimeZone classes aren't in the 5.1.6 sources (but the timezone functions are). I'm guessing some distros either backported this feature or used a post-5.1.6 SVN shapshot.
(In ) fixes #1359 - use procedural interface instead of DateTime & DateTimeZone classes to support php 5.1.6 with experimental date support enabled