private String daysToString(Collection<? extends Integer> days) {
		StringBuilder sb = new StringBuilder();
		for(int d : days) {
			switch(d) {
			case MONDAY:
				sb.append("M ");
				break;
			case TUESDAY:
				sb.append("T ");
				break;
			case WEDNESDAY:
				sb.append("W ");
				break;
			case THURSDAY:
				sb.append("R ");
				break;
			case FRIDAY:
				sb.append("F ");
				break;
			}
		}
		return sb.toString();
	}