Posting date changed without user interaction

Hi Guys
When users enters posting date on item journal like Nov. 01/2017 tries to post in and the posting date range is Nov 01…30, the system pops up posting date is not allowed flag, but it is still open the whole month for that user and also the g/l setup is also open for the whole month and when the item journal is opened by different user other than the one who created it is found to be like Nov 11/2017, without no one touching it.It is weird.Does anyone encountered this error before ?.

NAV 2015 W1 8.037874.0

Check the Allowed posting from and Allowed posting to fields in the User setup table. If the posting date is within these 2 days then it will allow to post the transaction for that particular date.