Calculating Previous Month(s) From Current Date

The following is the script I used to perform a simmaler task.

// Get date from field

var v = getField("add your reference date field name here").value;

// Get the field values, as numbers

var d1 = getField("add your field name").value;

if (v && d1) {

    // Convert string to date

    var d = util.scand('mmmm/dd/yyyy', v);

    // add d1 as days

d.setDate(d.getDate() + d1);

    // Set this field value to the new date

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

} else {

    // Clear this field

    event.value = "";

}

Unfortunately the numbers of days in a month or year are not the same for all months or years, so the get and set date methods might not work. Fortunately there are the getMonth() and setFullYear() methods for getting or setting the month or year for a given date.

For the "On Blur" action for the "DateField" you can use:

function GetField(cName) {
// get a field object with error catching;
var oField = this.getField(cName);
if(oField ==  null) app.alert("Error accessing field named: " + cName, 0, 0);
return oField;
} // end GetField function;

function AddMonths(oDate, nMonths) {
// add nMonths to oDate object;
oDate.setMonth(oDate.getMonth() + nMonths);
return oDate; // return adjusted date object;
} // end AddMonths;

function Scand(cFormat, cDate) {
var oDate = util.scand(cDateFormat, event.value);
if(oDate == null) app.alert("Error converting " + oDate.valueAsString + " with format: " + cDateFormat, 0, 0);
return oDate;
} // end Scand functon;

var cDateFormat = "mm/dd/yyyy"; // format for date strings;
// event value is the start date string;
// 12 months ago;
var o12MonthsAgo = GetField("12MothsAgoDateField")
var oDate = Scand(cDateFormat, event.value);
oDate = AddMonths(oDate, -12) // subtract 12 months;
o12MonthsAgo.value = util.printd(cDateFormat,oDate);
// 18 months ago;
var o18MonthsAgo = GetField("18MothsAgoDateField")
oDate = Scand(cDateFormat, event.value);
oDate = AddMonths(oDate, -18) // subtract 18 months;
o18MonthsAgo.value = util.printd(cDateFormat, oDate);
// 36 months ago;
var o36MonthsAgo = GetField("36MothsAgoDateField")
oDate = Scand(cDateFormat, event.value);
oDate = AddMonths(oDate, -36); // subtract 36 months;
o36MonthsAgo.value = util.printd(cDateFormat, oDate);
// and so on;

Since getting a field object, converting a date string to a date object and adjusting the date object using the getMonth and setMonth methods are repeated several times I have used functions so the repeated code could be reused.

If you really don't want to go in details (or not have time to do that)

Here is the simple solution of your problem.

I have written a small function (a few lines)

Put this in document level javascript

// Document level javascript function -----

function getPastDate(textFieldName, months){

var cDate = util.printd("mm/dd/yyyy",new Date(this.getField(textFieldName).value));

var sDate = util.scand("mm/dd/yyyy", cDate);

          if ( sDate== null ){

                    app.alert("Please enter a valid date of the form \"mm/dd/yyyy\".")

          }else {

          var pDate = new Date(sDate.getFullYear(),(sDate.getMonth() + months),sDate.getDate());

          return util.printd("mm/yyyy",pDate);

          }

}

Now suppose we have a textbox name "Text1" having date with format "mm/dd/yyyy"

1st parameter is for textbox name (having the date you want to process)

2nd parameter is number of months (to subtract pass a negative value)

If you want to get result in another textbox "Text2" write the code below in the calculate event of Text2

event.value = getPastDate("Text1",-12);

// This will subtract 12 months from "Text1" value

Hope this will help