Seeking Pdf form help - javascript formula to auto-populate fields based on data from other fields.

Question

Hi there, I am new to PDF form work, and am wondering if someone could help me with a javascript formula.
I want to auto-populate the EXPIRYDATE field, as the same date as the entered AUTHORIZATIONDATE field, but 4 years later.
So, I want to be able to enter 11/14/2014 in the AUTHORIZATIONDATE date, and have 11/14/2018 auto populate in the EXPIRYDATE field.
Seems simple I know, but I've messed around quite a bit and can't seem to make it work. Is this possible??
Any help would be very much appreciated!!

Answer 1

And what have you done?
This can only be done with custom JavaScript programing.
The value of date type fields are text field and not numeric data. The first task is to convert the dates to a number on some type of number sequence that is a mapping to dates.
Have you looked at the Acrobat JavaScript API Reference, the MDN JavaScript reference?
I would use the Acrobat JavaScript util.scand to covert the date string to the number of milliseconds from January 1, 1970 midnight. and then use the getFullYear method of the date object for the year value and add 4 years to that value and then use the setFullYear method to set the year for the date object. Now you can use the util.printd method to format the date object as a date string with a specific format.
// get the date value, format of date string and years to add;
var cDate = "11/14/2014"; // date value;
var cFormat = "mm/dd/yyyy"; // date format;
var nYears = 4; // years to add;
// convert date string to date object;
var oDate = util.scand(cFormat, cDate);
if(oDate == null) {
app.alert("Error converting " + cDate + " using format " + cFormat, 0, 1);
// add years to date object;
oDate.setFullYear(oDate.getFullYear() + nYears);
// display result;
var cExpireyDate = util.printd(cFormat, oDate);
app.alert("Authorization Date: " + cDate + "." +
"\nExpire Date: " + cExpireyDate, 3, 0);