there is no need to add the `? true : false`...  `(endDate.getTime() - startDate.getTime() > 86400000)` already returns a boolean.

also, I don't think this logic is correct. event might start at 11pm and end at 1am.. you actually need to check if they are the same day. Use [`Calc.isSameDate`](https://github.com/mozilla-b2g/gaia/blob/master/apps/calendar/js/calc.js#L382-L395) instead.