Date arithmetic in Informix Online 5.0

I'm trying to do some basic date math in informix online. I have a table with a column called 'access_date' which has a date column stored as '20000702' for todays date. I'd like to be able to generate queries where I can say "look at all events which have happened XX days from today". (e.g. 20000702-90 would be 3 months ago) I know in mysql there is a command called DATE_SUB which does this, is there an equivalent in informix, particularly in Online version 5? (I know, I know, it's an OLD version, but the customer won't upgrade). Thanks in advance!! Zack