A very common situation is when reporting is off due to system day being wrong.  Go to manager - reports - past system days.  Run a report for area in question.   Make sure to add and remove a few days to both the suspected day you're looking for.    For instance if there's an issue on the 23rd search from the 17th to the 28th.  

Look at the list the follows for the date selection.   System day will be on the left followed by the start and end time for that day.   Look at the times and change the system day if necessary.