I have a custom Sharepoint list which I'm using as an team absence calendar. One of the fields is the Start Date. I've created a Flow triggered by an insert to the list which posts a message to a Yammer group:

The problem is that the Start Date is off by one day in the Yammer message. If I create the entry in SharePoint with a start date of 2017-02-17, the Yammer message shows 2017-02-16.
Is this a bug, or somehow related to some other configuration setting such as timezones?