public static String formatDurationInMinutesAndSeconds(final long milliseconds) {
        if (milliseconds < 0) {
            return "?:??";
        }
        final long minutes = ((milliseconds + 500) / 60000);
        final long seconds = ((milliseconds + 500) / 1000) - minutes * 60;
        return minutes + ":" + (seconds < 10 ? "0" : "") + seconds;
    }
Formatting of the hidden date of a cache

@return {@code null} or hidden date of the cache (or event date of the cache) in human readable format
main/src/main/java/cgeo/geocaching/utils/Formatter.java