I have been moved to 12 hour shifts, & I notice that Qalendar has an issue with events that span over midnight.

For example, if I try to schedule an event from 1800 hours to 0600 hours, Qalendar sets the beginning & ending time to 0600. To work around, I have been scheduling events that span midnight as 2 events; for example: 1800 to 2359 on one day, & 0000 to 0600 on the next day.

I must join in the chorus of praise for Qalendar, thought! It's one of the reasons I still use the N900 as my primary phone!