When did prince Albert invent Christmas cards?

He did not. His Highness did introduce the pre-existing custom of Christmas Trees into UK, that is known. ( Dickens did not like the idea.). Sir Henry Cole came up with what we now call Christmas Cards in the late l840"s or maybe l85l about the same time. Stamps as we know them were not introduced until the l840"s which may explain the lag. Phones, let alone cell-phones were far in the future.