Have you looked into Moment.js? http://momentjs.com/ It's a handy date-object wrapper that makes date object manipulation easy. Particularly, the local() function provided will give you what you need here.
All you have to do is install moment from npm and then include it in your js file at the top like this:
var moment = require("moment");
Then to change your time_utc variable to local all you have to do is:
var time_utc="2016-04-25 20:19:00.307";
document.write("Local date:"+moment(time_utc).local());
As someone advised me before, it is not wise to include an entire library for a simple, one time function. As a disclaimer, my work requires me to do many date-time calculations and conversions throughout a large project, so including a library for ease is much preferred in my case. However, if you only have to use it this one time, my answer may not be the best.