I know, Mozilla is responsible for Sunbird, but it may be me, too.
So, I have discovered that if I set Sunbird to display events in the 'Currently Selected Day,' it will actually display the events of the previous day (the one before the selected day). If I set it to display 'Today's Events' (or seemingly, any setting other than 'Currently Selected Day') it does what is expected.
Anyone else encountered this? Or have I screwed something up (quite possible).