How to calculate multiple future dates from one date

I am trying to enter a single pay period start date that leads to the start and end dates for the next 27 pay periods.

for the starting pay period I used the following script in each text field cusom calculation script adjusting the field to pull from

var d = util.scand("mm/dd/yyyy", this.getField("PPWK2End1").valueAsString);

var theTime = d.getTime () ;

var oneDay = theTime + 1*24*3600*1000;

var dd = new Date(oneDay);

event.value = util.printd("mm/dd/yyyy", dd);

then I used the following to get the payperiod end date 

var d = util.scand("mm/dd/yyyy", this.getField("PPWK1Start2").valueAsString);

var theTime = d.getTime () ;

var oneDay = theTime + 13*24*3600*1000;

var dd = new Date(oneDay);

event.value = util.printd("mm/dd/yyyy", dd);

The problem is that the dates do not populate beyond the second pay period and the calculations seem to forget there are 31 days in october when it does run correctly.

Please help! there has to be an easier way!