When I open a chart for an item with some data, the graph is displayed correctly. I can set the period for almost two years (~1y 11m 29d) and the graph is still displayed correctly. But, when I press "All" and the period is set to 2 years, the graph is rendered empty. For some reason, after pressing "All" the "stime" parameter of the graph URL is set to "20010401220359". This value is also remembered in the profiles table and opening the latest data page again sets the timebar to year 2001.
The broken graph URL looks like this: /chart.php?itemid=26452&period=63072000&stime=20010401220359&updateProfile=1&profileIdx=web.item.graph&profileIdx2=26452&sid=7d887b55052a47b3&width=1087&curtime=1399891905821