Typically, the process will use the date of the timesheet to calculate the year and period it is to be posted to based on the user's permissions which are managed via their Security Profile. Therefore, if a user does not have permission to post to the Timesheet's period, it will go to the nearest open period that they can post into. For more information about posting to future or restricted periods please see the article How to set future or working period posting permission for users.
Timesheets can be posted via Financials and so it should be possible to post a reversal and then repost into the correct period. However, if you require further assistance, please raise a new case online and reference the title of this article.
Posted timesheets in Financials showing in the wrong period in Costing module
Updated over a week ago