You can do append 'T00:00:00.000Z' to make the time zone specific (Z indicates UTC)
new Date('2015-08-27' + 'T00:00:00.000Z')
Note that new Date('2015-08-27') is treated differently in ES5 (UTC) vs. ES6 (Local), so you can’t expect it any correction to be work consistently if you were planning to to hard code it (i.e. don’t do it)
Also, do note that your console.log might show you the local time corresponding to the UTC time the expression evaluates to (that tends to throw you off a bit if you are expecting UTC to be at the end for expression that evaluate to UTC times and your local time zone at the end for those that evaluate to your local time). For instance
new Date('2015-08-27T00:00:00.000Z')
could show
Thu Aug 27 2015 1:00:00 GMT+100
which is the same as
Thu Aug 27 2015 00:00:00 UTC