В объекте c
double timeStamp = 1513330403393;
NSTimeInterval unixTimeStamp = timeStamp / 1000.0;
NSDate *exactDate = [NSDate dateWithTimeIntervalSince1970:unixTimeStamp];
NSDateFormatter* dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = @"dd/MM/yyy hh:mm a";
NSString *finalate = [dateFormatter stringFromDate:exactDate];
In Swift
let timeStamp = 1513330403393
let unixTimeStamp: Double = Double(timeStamp) / 1000.0
let exactDate = NSDate.init(timeIntervalSince1970: unixTimeStamp)
let dateFormatt = DateFormatter();
dateFormatt.dateFormat = "dd/MM/yyy hh:mm a"
print(dateFormatt.string(from: exactDate as Date))