I made an event in Calendar for October 23rd through November 5, 2016. It shows I entered those dates but the graphical bar is showing a start date of October 16th. If I switch to any other start date it appears ok. It's just for October 23rd. Anything I enter for 23 October shows up on the Calendar starting the 16th.
It shows fine on my iPad and iPhone but not on my laptop.
MacBook Air (13-inch Mid 2011), OS X El Capitan (10.11.6)