error -1267, interval, extends

Hello, The select is : Select CURRENT,enc_cce,enc_ccp,201,0 from vte_enc where EXTEND(enc_date_dern_liv,year to day ) < (Extend(TODAY ,year to day )- interval (0-03) year to month ) and (enc_date_dern_liv>mdy(1,1,'0001')) and (enc_prf_stk > 0 OR enc_prex_galva >0 OR enc_prex >0 ); And I receive this error yesterday (30/may/2000) and today : 1267: The result of a datetime computation is out of range. The datatype of the field "enc_date_dern_liv" is "date". I understand that when calculating, Informix obtains a date who is invalid (30/feb/2000), but I didn't find how to change the select to convert in the right way. I read manuals, but it doesn't helped me a lot. Of course, a workaroud is to test "today - 90", which is approximatively correct, but it's more accurate & elegant to test "today - 3 months" Can anybody help ?? Thanks in advance Ben