public String getAccumulatedDuration() {
        StringBuilder duration = new StringBuilder();
        
        // hours
        duration.append(String.valueOf(getAccumulatedHours() ));
        duration.append(":");
        
        // minutes
        duration.append(String.valueOf(getAccumulatedMinutes() ));
        duration.append(":");
        
        // seconds
        duration.append(String.valueOf(getAccumulatedSeconds() ));
        
        return duration.toString();
    }