Edit dialog doesn't handle BCE dates
The current event-edit dialog is not able to edit BCE dates (to be more exact even dates before 1752 can not be entered). This is a todo on my list, but needs an expansion of the standard date widget of wxwidgets. To 'enter' BCE events, the only way currently is not to use the edit dialog, but use right mouse button drag to create an event (zoom to 400 BCE, and drag an event by right mouse button into the view. Correct the start and end date by left mouse button dragging of the border. The exact date is shown in the status line while dragging to allow better adjustment).
The only other way to really enter dates BCE is to use an simple editor and go for the ics file directly.