Date manipulation in JavaScript

Modern JavaScript (Node.js)

function ConvertTime_Node(dateStr)
{
	let dateObj = new Date(dateStr);
	
	// Convert 5 hours 30 minutes to milliseconds
	const hoursToAdd = 5;
	const minutesToAdd = 30;
	var millisecondsToAdd = hoursToAdd * 60 * 60 * 1000 + minutesToAdd * 60 * 1000;

	// Change time
	dateObj.setTime(dateObj.getTime() + millisecondsToAdd);
	
	// Format
	let options = 
	{ 
		year: 'numeric',
		month: 'numeric',
		day: 'numeric',
		hour: '2-digit',
		minute: '2-digit',
		second: '2-digit',
		hour12: true
	};
	const formatter = new Intl.DateTimeFormat("en-US", options);
	const result = formatter.format(dateObj);

	return result;
}

Microsoft JScript Version (WScript)

function ConvertTime_WScript(dateStr)
{
	var dateObj = new Date(dateStr);
	
	// Convert 5 hours 30 minutes to milliseconds
	var hoursToAdd = 5;
	var minutesToAdd = 30;
	var millisecondsToAdd = hoursToAdd * 60 * 60 * 1000 + minutesToAdd * 60 * 1000;

	// Change time
	dateObj.setTime(dateObj.getTime() + millisecondsToAdd);
		
	// Format
	var month = dateObj.getMonth() + 1; // Months are 0-based in JavaScript
	var day = dateObj.getDate();
	var year = dateObj.getFullYear();
	var hours = dateObj.getHours();
	var minutes = dateObj.getMinutes();
	var seconds = dateObj.getSeconds();
	
	// Format the hours to be in 12-hour format and get the AM/PM part
	var ampm = hours >= 12 ? 'PM' : 'AM';
	hours = hours % 12;
	hours = hours ? hours : 12; // the hour '0' should be '12'
	
	// Pad the minutes and seconds with a zero if they are less than 10
	minutes = minutes < 10 ? '0' + minutes : minutes;
	seconds = seconds < 10 ? '0' + seconds : seconds;
	
	// Format the date string
	var result = month + '/' + day + '/' + year + ' ' + hours + ':' + minutes + ':' + seconds + ' ' + ampm;	

	return result;
}