/* is series date only */
isdate(s = refwindow(w0))
{
        local status = FALSE;

        if (isarray(s))
        {
                if (length(s) > 0)
                {
                        /* check units */
                        status = isdate_iterate(s);
                        status = transpose(status);
                        status = all(status);
                }
        }
        else
        {
                /* string */
                status = isdatestr(s);
        }

        return(status);
}


/* iterate through columns */
ITERATE isdate_iterate(s)
{
        local vunits, status;

        /* use Z units to get date for each column */        
        vunits = tolower(getzunits(s));

        status = (vunits == "date");

        return({status});
}