Scratch that. I have an answer for you. You need to be explicit with the date for p24m+2 using the inline modifier ^ GDFILE = testprecip1129.grd + testprecip1130.grd GDATTIM = 1200 GLEVEL = 0 GVCORD = none PANEL = 0 SKIP = 0 SCALE = 999 GDPFUN = add(p24m,p24m+2^141130/1200) -Michael Ticket Details =================== Ticket ID: SGQ-682303 Department: Support GEMPAK Priority: Normal Status: Open