Fighter plane extraordinaire, the Spitfire – star of the Battle of Britain – turned 90 this year. One former RAF air controller described the aircraft as epitomising “the spirit, backbone and sheer bloody-mindedness of a tiny island whose people would not give up and would never surrender”. Rousing stuff.

There have been other rheumy-eyed retrospectives too. Queen Elizabeth II was born 100 years ago this year, and it has plausibly been said of her late Majesty that she represented the very last stable myth of this nation.

Beyond these shores, this year marks 250 years since the founding of the United States of America, and 25 years since the attacks of 9/11. Two very different kinds of anniversary, for sure. But both have come freshly into view over the last few months, since the war with Iran.

The word “anniversary” comes from the Latin anniversarius, meaning “returning yearly”. It names those moments in the year when time circles back on itself. Originally, in medieval Christian usage, anniversaries referred to a death: an anniversary Mass. But arguably, even the most joyful commemoration is a kind of mourning, in recognising that something has now passed into history.

Perhaps that sounds a bit bleak. But I make the observation with feeling, as someone who’s just turned fifty. I marked that personal milestone with a dinner that brought together loved ones from each decade of my life: earliest school friends; others from university, work, and beyond; my three daughters too, who are (to my slight astonishment) now grown up enough to help host.

It was wonderful. But taking stock at my fiftieth, it struck me that all anniversaries, whether public or private, involve a curious kind of double vision. They obviously ask us to look backwards, which can be a heady business, given that even sharing happy memories may be a way of feeling sad, for reminding us of good times now gone.

Less obviously, though, anniversaries invite us to look forwards. They’re more than an occasion for nostalgia or handwringing. Recollection is also about reckoning. By pausing our ever-hectic lives, anniversaries allow us to think about the future through lessons we have learned from the past: as individuals, a society, a whole human race. They might, in that sense, be seen as calendared response to the psalmist’s prayer: ““Teach us to number our days, that we may gain a heart of wisdom”.

Remembering may fill us with gratitude or regret, but it also sharpens our sense of what’s still worth doing and preserving – as well as, what is yet worth striving for.