There are … weeks until Christmas. Days are satisfying to count, but weeks are how life is actually organised: paydays, school terms, delivery slots and weekends all run in weeks, so this is the number that turns a countdown into a plan.

We work the figure out from the exact day count — … days remain until 25 December — divided by seven and rounded up. Rounding up is deliberate: if three days of a week remain, you still have that week's shopping, posting and wrapping to fit in, and it would be a shame for a countdown to pretend otherwise.

Try giving each remaining week a job. With plenty of weeks left, one can be for lists and one for ordering the things that sell out. The middle weeks are for deliveries, cards and the big food order. The final week — which begins on 18 December — is best kept for fresh food, batteries, wrapping and absolutely nothing new. Advent itself starts on …, which is a good natural line for "decorations up" week.

However you slice it, the weeks fall faster than the days seem to suggest. Check the number whenever you need a nudge: it drops by one every seven days, every week of the year, and the moment one Christmas passes, the count to the next one begins.