You might be interested in the eXtreme CL category of Date and Time commands.
this article explains how to work with variables.
DCL VAR(&AREA) TYPE(*CHAR) LEN(4) VALUE(BOOK)
CL doesn’t have a DATE data type, so you can’t. The closest you can get is a *CHAR variable that is big enough to hold whatever date characters you want to put in it.
If you need to process DATE variables with date functions, don’t use CL. It’s not a data processing language — it’s a job control language.