When selecting a time range from example: "April 11, 2014" to "April 14, 2014" is the date tooltip to the right showing "April 15, 2014" . I was expecting "April 14, 2014" . I have not been able to find any function to change/offset the end date.
Please take a look at eventEndSpec property:
You can also customize the tooltip HTML directly using onTimeRangeSelecting event handler (args.right.html):