I love the tool because it really helps me stay better organized. I am pretty busy and have to keep track of many events, tasks, and also other people activities. What I am getting into is when I have to move an event from one day to another, it often collides with others already scheduled for that day. I think it would be awesome for Rainlendar to warn me (other users as well of course - I am not that selfish ) that task I attempt to move is overlapping with already existing on that day. The feature may be tricky but 4 possible options (radio buttons or sth):
- put as first on that day (does not affect other tasks that day
- earlier available time slot on that day
- shift existing overlapping event and others to earlier time
- shift overlapping event and others to later time
- later available time slot on that day
- put as the last on that day

Some kind of note from collisions might be possible. I'd have to add support for the free/busy time in the iCalendar format. Moving the events automatically most likely is not going to be implemented as it gets quite complex with recurring events.