If you’re struggling to find an Advent calendar with even a glimpse of the Nativity scene this year, it could be because they’ve been ousted from the high street by Christmas calendars made for pets.David Marshall, founder of the Meaningful Chocolate Company, estimates that this year only 400,000 Christian-themed calendars have gone on sale in Britain – as opposed to more than a million stuffed with treats for pets, like catnip and dog biscuits. But with just over a week left until the start of Advent, there is still time to buy a religious calendar. Marks and Spencer stores are selling a colourful calendar featuring a crib, shepherds and wise men, whose windows hide pictures about the nativity story – and chocolates – for £2. John Lewis has a paper cal