Financial Calendar dates reverting?

Can someone explain if there is a point where the financial calendar dates would get automatically updated (ie: closing last period in previous year, etc.)? We've had an issue 2 years in a row where our finance department swears the calender is set up correctly for the new fiscal year and then the month and day for the new fical year periods magically revert back to the previous years month and day settings. As you can imagine, this causes grief since some periods had entries that could not be moved. Lawson advised us to paint a screen to fix the date in GLSYSTEM which seems to have worked. It's hard for me to imagine that Lawson would overlay the calendar without warning if you have the new set up. Thanks for any info!