I upgraded to 0.6 yesterday.
Today it shows me on the visits by server time graph an visitor for the 23rd hour while server time is nowhere near that yet. (see attachment)
Keywords: 23h, visitors, graph
Attachment: visitors by server time showing visitor in the future
piwik-future.png
To reproduce just insert something like this into your database:
INSERT INTO foo_log_visit
VALUES(31678, 3, '17:49:38', 'be47a2199e0cb3a6e4e15b4aa049189f', 1, '2010-05-06 23:49:43', '2010-05-07 00:01:19', '2010-05-06', 823, 371, 34, 696, 0, 1, ,, '', '2522d67bafe2a77a8631dbb672c725d9', 'AND', 'AN', '3.1', '800x480', 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1119446556, 'en-us', 'us', 'amn', 'Ip');
This is the actual culprit in my case. Verified by changing visit_last_action_time to '2010-05-06 23:49:59' and then checking the stats.
Shame on you for not checking for visits across boundaries. m(
(In [2156]) Fixes #1338 Visits in Piwik are defined by the last action datetime. Visits by server time used to report by entry visit time, and would therefore report visits that started at 11PM and carried on until midnight the requested day.