* java.util.Date, int, int, long)
*/
public Errors update(final Date start, final Date end, final int iterationPersistanceId, final long iterationPersistanceVersion) {
// find the iteration to update
Iteration iteration = iterationRepository.findByPersistanceId(iterationPersistanceId);
// if iteration is found
if (iteration != null) {
// update the iteration object
iteration.setEnd(end);
iteration.setPersistanceId(iterationPersistanceId);
iteration.setPersistanceVersion(iterationPersistanceVersion);
iteration.setStart(start);
// validate
Errors errors = iterationValidator.validate(iteration);
// if there are no errors, persist iteration