On a Friday evening in May 2018 I am going to see the Broadway show Hamilton. We had to book the tickets two weeks ago. Fair enough, you might say — some theatre tickets sell out long before rehearsals have begun. Nonetheless, it seems a madly long way off and what if I forget about it between now and then?

This week I’ve tried to pencil in the cinema with a group of friends — no one was free until April — and Saturday supper with a couple: they couldn’t do until July.