Sure Peet.
First of all here is a useful link for Date object in JS: http://www.w3schools.com/jsref/jsref_obj_date.asp
Here is a code example I have executed in Eval JS step in TC:
//current time print
var d = new Date();
LR.log(d.getHours() + ":" + d.getMinutes());
//current time + 40 minutes offset
d.setMinutes(d.getMinutes() + 40);
LR.log(d.getHours() + ":" + d.getMinutes());