Incorrect date given by Siri
I've just downloaded the new MacOS Sierre application onto my MacBook Pro. I've picked up that Siri is not giving me the correct birthday date (in most case a day earlier is given by Siri) For example I've put a birthday date of 16 April 2003 on my Contact list of a person then I go and ask Siri when is this persons birthday, Siri will give me 15 April 2003. This is happening to all of the dates that I've loaded.
MacBook Pro (Retina, 15-inch, Mid 2015), OS X El Capitan (10.11.6)