Hi, Most of the major stores publish details on their websites...for Carrefour check carrefouronline.com
This link will take you to the opening hours for festivals.
Check 'Buscar la tiendas' for your local hypermarket/supermarket; the full details for your local store appear on the front page of the selected store. Note however that at the moment they only cover up to and including Dec 20th. I do know that they are open from 1000-2200 everyday including Sundays until and including Christmas Eve. They are also open on Sun 28th.
Dont know about other shops...check store websites is probably the best advice...
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