Regarding Denodo Platform 6.0, you have to specify a specific time zone while creating a base view. That means all the dates coming from the data source would be associated with the base view's time zone. In your case, as your data source provides dates belonging to two different timezones, my recommendation is adding/subtracting the necessary amount of hours to one of these columns (by editing the desired column) while creating the base view in order to have all the dates in the same time zone.
However, the Denodo Platform 7.0 version includes among other date types the TIMESTAMPTZ date type which maintains the information about the date's time zone. So, if you are working with the Denodo Platform 7.0 version, my recommendation is creating the base view and making sure that the date type used for these two date columns is TIMESTAMPTZ.
Hope this helps!