Date field difference calculation

Question

Hi all,
I am new to Adobe and Java scripting so apologies if this has already been answered elsewhere - I have not been able to find it if it has.
I want to calculate the difference between two dates fields in hours and mins on a form.
I have two fields, both Date format (dd/mm/yyy HH:MM), a Start and End date and I want the difference between them in the Time format HH:MM.
Can anyone help me with the script for this? What I have so far is:
var strStart = this.getField("StartTime").value;
var strEnd = this.getField("EndTime").value;
if(strStart.length || strEnd.length)
var dateStart = util.scand("dd/mm/yyyy HH:MM",strStart);
var dateEnd = util.scand("dd/mm/yyyy HH:MM",strEnd);
var diff = dateEnd.getTime() - dateStart.getTime();
// One Day = (24 hours) x (60 minutes/hour) x
// (60 seconds/minute) x (1000 milliseconds/second)
var oneMin = 60 * 60 * 1000;
var mins = Math.floor(diff/oneMin);
event.value = util.printd("HH:MM",mins);
But this is not working...
Mary

Answer 1

The result can be formatted using:
// format result using "h:MM" format
event.value = util.printf("%,0 0.0f" + ":" + "%,002.0f", nHours, nMinutes);
One cannot use the date or time formats since the time values will be limited to the hours and minutes values for 1 day, so any time value that is over 23 hours 59 minutes is not possible.
A full script solution including document level functions for conversion of date strings to minutes and converting minutes to a time string:
// reusable document level functions;
function Time2Num(cFormat, cDate) {
// convert date value with format to number of minutes form Epoch date;
var oDate = util.scand(cFormat, cDate);
var nMins =  null;
if(oDate ==  null) app.alert("Error converting " + cString + " using " + cForamt);
else nMins = oDate.getTime() / (1000 * 60);
return Math.floor(nMins);
} // end Time2Num format
function Num2Time(cFormat, nMins) {
// convert number of muniutes to h:MM or HH:MM format;
// return formatted string for valid formats;
// return null for invalid formats;
var cElapsed = null;
// test for nMins being a number;
if(isNaN(nMins)) {
app.alert("Minutes must be number",0, 0);
} else {
var nHours = Math.floor(nMins / 60);
var nMinutes = Math.floor(nMins % 60);
switch(cFormat) {
case "h:MM":
cElapsed = util.printf("%,0 0.0f" + ":" + "%,002.0f", nHours, nMinutes);
break;
case "HH:MM":
cElapsed = util.printf("%,002.0f" + ":" + "%,002.0f", nHours, nMinutes);
break;
default:
app.alert("Invalid format " + cFormat + "\nMust be \"HH:MM\" or \"h:MM", 0, 0);
break;
return cElapsed;
} // end Num2Time function
// end document level funcitons;
// custom calculation script;
event.value = ''; // clear result;
var strStart = this.getField("StartTime").value;
var strEnd = this.getField("EndTime").value;
if(strStart.length || strEnd.length) {
var nDateStart = Time2Num("dd/mm/yyyy HH:MM",strStart);
var nDateEnd = Time2Num("dd/mm/yyyy HH:MM",strEnd);
var nMins = nDateEnd - nDateStart;
// format result using "h:MM" format
event.value = Num2Time("h:MM", nMins);
// end custom calculation script;