Trouble with date compuation

Hi, I have a little problem with date computation. The problem is how informix handle this field. I mean I have a function like this: function name() define a date, b date let a = today let b = today -3 units month return a,b end function It works correctly if the monts is less or equal 30 day (February,April, June ecc.. ) but if the month is of 31 days I receive , at the 2nd let instruction, a FORM STATEMENT ERROR -1267 The RESULT OF A DATETIME COMPUTATION IS OUT OF RANGE. I have tried with this statement: let a = 30/07/95 let b= a - 3 units months ... and it works but if I use : let a = 31/07/95 let b = a -3 units month I have the error. ( I think he calculate 31/04/95 and then he check for error in date field) I had to write a little function to walk around this problem but sometimes I can't use it (The function work for calculate the expiring date of a bill , and not to calculate any end of month ) I'm using I-4gl (RDS) 4.10.UE2 and SE 5.00.UD1 Any idea ????? P.s. Sorry for my not good english. Pierluigi "Pigi" Frullani pigi@frumar.it