HI, I am using jasper5.6.1 in win7,jdk1.7, I use days function in studio to calculate date diff between min_date and max_date, such as : days($V{min_date},$V{max_date}) it works fine in studio, but when I called it from web java application, it always return me following error: net.sf.jasperreports.engine.fill.JRExpressionEvalException: Error evaluating expression : Source text : DAYS($V{min_date},$V{max_date}) I also encountered another IF experession error, I doubt it's java issue, and I check my report language setting, it's "JAVA". if I cannnot use system function, I have to pass all calculated varibles from outside application, it's too complex. could you give me some suggesiton? thanks!