Convert longs (time_t in UNIX terminology) to seconds

public class Main {
  public static void main(String[] args) {
    System.out.println(msToSecs(1000));
    System.out.println(msToSecs(1100));
    System.out.println(msToSecs(1024));
  }

  /** Convert a long ("time_t") to seconds and milliseconds */
  public static String msToSecs(long t) {
    // The first attempt fails for the case "1024"
    //return t/1000 + "." + t%1000;

    return Double.toString(t / 1000D);
  }
}