editing a date should be handled differently, by klicking on a date just the month or day or year should be marked, so you can easyily change this alone (Right now klicking on a date marks the whole date).
Editing a timeline item, there is no finishing editing button, you just have to klick on the item to finish editing. this seems to me something out of the row comparing to other mac programms (comparing for example to iCal).
Overall seen it's a very cool program