There is a quite noisy discussion going on in Germany right now, because christmas eve is a Sunday, and there is a limited number of Sunday shop openings in Germany. For Berlin, the list is here, and christmas eve is not on the list, elsewhere it is.
I am pretty confident that my supermarket will be open on December, 24, and of course on December, 26. It was open on Whit Monday this year, as shown above. Germany is weird (by law, GG 140 -> Art 139 Weimarer Verfassung).