My friend just told me about a dinner party she and her husband threw last weekend. The invitation gave the start time as 7pm, with dinner served at 8pm. Most of the guests showed up from 7 on, allowing them time to mingle and enjoy a glass of prosecco while dinner was prepared.

Unfortunately, one couple didn’t turn up until a quarter to 9. Just when my friend was putting the finishing touches on dinner, she got a text saying they were just now leaving the house. Clearly, they didn’t understand that a dinner party start time isn’t flexible! My friend ended up holding off serving dinner until everyone arrived, at which point her guests were starving—all because one couple couldn’t be bothered to leave on time.

With some parties, the start time is a bit flexible. If a cocktail party starts at 7, it’s fine to show up at 7:20. Many celebrations are the sort where you can pop in and out. But dinner parties are different. They require a lot of preparation and the timing must be as accurate as possible. The host may have a kitchen emergency that causes a delay, but the guests shouldn’t be a source of concern. If they say dinner is going to be served at 8, you’d better be in your chair by 8.

And, of course, do bring a bottle of wine or some other token for your host. It’s just good etiquette!