Because of the way you have to take all of the documents that will be submitted to the Auditor, therefore, if the date 27/05/2558 (2015) auditor cannot audit the financial statement immediately as required by law.
Because you have to take a good look at all the documents will be sent to the auditor, so if you set the date 05.27.2558 auditor can not audit the financial statements on time as required by law.
Because you have to take the time to find all the documents to be sent to the auditor, so if it set the date 27 / 5 / 2558 auditors cannot verify the financial statements in time according to the law.