Are you having issues not being able to change the work date in Microsoft Dynamics NAV 2018? If so, it's most likely because the company you are working with was copied from a Cronus database.
What is Work Date in NAV? Work Date: Sets and returns the work date for the current session. (This function returns the work date chosen using the Work Date option on the Tools menu. If the user did not choose a work date, the the current system date is returned.)
When you create a company by copying the Cronus database there's a field titled "Demo Company" that comes standard as Editable "No". This auto populates the work date to the last General Ledger Posting Date. In order to fix this you have change the "Demo Company" Editable to "Yes".
Where is the field "Demo Company" located? Well, you will not find this field on the actual Company Information page but rather on the Company Information Table. Once the Editable is changed to "Yes" you can then add this field to the Company Information Page or just run the page to uncheck this box.