Time Zone Applied in UI Format

Talking about Date, it is meaningless without definition of timezone.
So, it is important to enable convert time between local and UTC.

Local Time -> UTC

// Create Date object for current location
var d = new Date();

// Get current time zone info
// Return offset unit by MINUTE
// For example: "UTC+8" = -480
var timeZoneOffset = d.getTimezoneOffset();

// Transform MINUTE to MILLISECOND
var offsetMsecs = timeZoneOffset * 60000;

// Obtain UTC time in msec
var utcTime = d.getTime() + offsetMsecs;

// Convert UTC time value to date string
var utcDate = new Date(utcTime);

UTC -> Local Time

// Input
var d,              // UTC Date Object
    timeZoneOffset; // Timezone Offset Minute (-480)

// Transform MINUTE to MILLISECOND
var offsetMsecs = timeZoneOffset * 60000;

// Obtain local time in msec
var localTime = d.getTime() - offsetMsecs;

// Convert local time value to date string
var localDate = new Date(localTime);