SimpleDateFormat

long timeInMilliseconds = 1454124312220L;
Date dateObject = new Date(timeInMilliseconds);

SimpleDateFormat dateFormatter = new SimpleDateFormat("MMM DD, yyyy");
String dateToDisplay = dateFormatter.format(dateObject);

fun Long.toDateString(dateFormat: Int = DateFormat.MEDIUM): String {
    val df = DateFormat.getDateInstance(dateFormat, Locale.getDefault())
    return df.format(this)
}