It seems dotproject has a nasty habit of forgetting the end date for a task, although it seems to calculate one based on task duration still. The task edit form won't let me set an end date after it vanishes. This might not be such a problem, but it causes the gantt chart view to fail - tasks with no fixed end date don't appear.

On the other hand, I seem to remember tasks appearing to be 1 day long on the chart at other times.

Ah, I see it's got something to do with how start and end times are set - I think I came across this - running with 24h time - I think it may be when I set the end time at midnight, the end date gets set to null.