Days until Christmas is the fun number. Shopping days is the useful one. There are … weekday shopping days left — the Mondays to Fridays between tomorrow and Christmas Eve — and every one that passes is one fewer chance to order, collect, wrap and post everything on your list.

We count weekdays only, on purpose. Weekday shopping days are when deliveries move, click-and-collect desks are staffed, lunch-break dashes happen and after-work trips get made. Weekends are lovely for browsing, but the machinery of Christmas runs Monday to Friday, so that is the number worth planning against. The count includes Christmas Eve itself — 24 December — as the final shopping day.

A simple way to use the number: split your list into thirds. Use the first third of the remaining days for anything ordered online or personalised, because postage waits for nobody. The middle third is for the high-street list and the food order. Keep the last few days for fresh food, forgotten batteries, wrapping paper and the one present you swore you had already bought. With … calendar days left overall, there is still time — the trick is not spending it all in the first category.

And if the number above looks alarmingly small, take heart: it looked the same last year, and Christmas still arrived fully wrapped. Check the Christmas Eve countdown for your true deadline, and good luck out there.