When you pass dates as a string, the implementation is browser specific. Most browsers interpret the dashes to mean that the time is in UTC. If you have a negative offset from UTC (which you do), it will appear on the previous local day.
If you want local dates, then try using slashes instead, like this:
var date = new Date('2006/05/17');
Of course, if you don't have to parse from a string, you can pass individual numeric parameters instead, just be aware that months are zero-based when passed numerically.
var date = new Date(2006,4,17);
However, if you have strings, and you want consistency in how those strings are parsed into dates, then use moment.js.
var m = moment('2006-05-17','YYYY-MM-DD');
m.format(); // or any of the other output functions