TR0528
The source value for a date category in a month level must be numeric. Also, it must be in the format MMDD, unless specified otherwise in the Date tab of the Column property sheet.
This error can occur if the source value for a date category was inadvertently changed or deleted.
Procedure
To resolve the problem, ensure that the Source
value on the General tab of the Category property
sheet uses the same date format as that specified on the Time tab
of the Column property sheet.