Natalie Haynes: Anniversaries are the marker buoys that help us navigate through life

Objectively, it doesn’t matter what date it was that the Titanic sank or Lincoln was assassinated

(Darren Diss)

For a lot of people, today is a very important day: 14 April 2012 marks the 100th anniversary of the sinking of Titanic, which is big news for reasons that aren't immediately obvious. Why does the sinking of a passenger ship a century ago still matter to us so much? Is it because of the huge loss of life? Surely not. Only 1,517 people died when Titanic sank: if we were concerned about numbers, we would instead be commemorating the 2,700 people who died in a Chinese earthquake on this day in 2010.

So is it the glamour of Titanic that compels us? It's been dramatised so many times (many of them silly, some of them with Celine Dion to add to the anguish), that we feel we know this story inside out. The pathos is undeniable: bright young things wearing beautiful frocks, mingling with an impoverished underclass, all trying to reach the same few lifeboats.

The Titanic story is one in which myth and legend have become so tightly wound – did the band really play on? Was it women and children first? Had the White Star Line really claimed the ship was "unsinkable"? – that it has almost reached a separate level of truth, in which the narrative matters more to most of us (other than the Titanoraks – a word I have happily discovered this week) than the facts.

But an undeniable fact about the whole affair is that it has had a dramatically higher impact on our news cycle today than either the death toll or the temporal distance can really explain. And the media is merely reflecting genuine public obsession: a memorial cruise even left Southampton 100 years to the day after Titanic did, full of high-paying passengers dressed in Edwardian outfits.

And given the enthusiasm for an anniversary in the media, those who aren't especially interested in Titanic have had a culturally deserted few weeks. By the time you'd switched off the Julian Fellowes programme (remembering in your irritation that Downton Abbey began with the sinking of Titanic, so it's not like you weren't warned), and discovered that the cinemas are showing a new 3D version of the James Cameron Titanic movie, you might have been tempted to go to see Battleship instead. And even that has ships sinking in it.

But you couldn't go and see football tomorrow to take your mind off it, at least not if you support Liverpool. Since the Hillsborough disaster on 15 April 1989, Liverpool have refused to play on its anniversary. While you might think this a perfectly reasonable response to a major tragedy, not everyone agrees. Alan Davies moaned about their behaviour on a podcast this week, because of the impact it has on other teams' schedules.

The predictable outcry went up. Davies's argument appeared to be that if Liverpool were going to mark the deaths of their own fans at Hillsborough, why did they not also mark the deaths of the 39 Juventus fans who died at a match against Liverpool on 29 May 1985? A spokesperson for the Hillsborough Justice Campaign confirmed that it had rejected the £1,000 donation Davies had offered to make, explaining, "While we accept his apology, we would prefer that he genuinely tried to understand why the decision never to play on the anniversary of the Hillsborough disaster is so important." But however crassly he made his point, doesn't Alan Davies ask a reasonable question? How long do we mark tragedies for? And how many of these anniversaries should we keep? Liverpool has maintained the anniversary of Hillsborough for 23 years now, but other football clubs don't do the same. Major football tragedies aren't so numerous that all teams couldn't mark all of them, and yet they don't. Does that mean they don't care, or does it just mean that they choose not to make a public statement?

When it comes to anniversaries, round numbers matter in the media far more than they do in real life. Last year's 11 September memorials were a big deal because it was the 10th anniversary. I suspect the 11th anniversary will receive far less coverage, and I bet the ninth anniversary did too. But a line has to be drawn at some point, when we shift from commemorating every year to every 10, or 50, or 100 years. Otherwise we would do nothing but remember losses every day, from every war, every disaster ever to befall humanity.

And media anniversaries aren't just negative. They're often marking events of social and cultural importance: battles, discoveries, legal rulings and the rest. In addition to the Titanic sinking, 14 April marks the completion of the human genome project (2003), the first edition of the Highway Code (1931), and the publication of The Grapes of Wrath (1939). Remembering these anniversaries is one of the ways we anchor ourselves to our history.

Objectively, it doesn't matter if it was on this day or another that Lincoln was shot by John Wilkes Booth, or that the Yorkists won the Battle of Barnet. But dates do matter to us – whether we are historians, trivia buffs or just holding out for a birthday gift. Without them, we're lost. Which is something that ancient historians knew perfectly well: Livy dated his history of Rome ab urbe condita – from the founding of the city – in 753BC. Everything else was measured according to when it all began.

My only plea in our mania for anniversaries today is that we try to expand our horizons to encompass more than one or two at a time. This coming July, for example, will mark the 75th anniversary of the deaths of Amelia Earhart, Guglielmo Marconi and George Gershwin, and the 75th anniversary of the births of Hunter S Thompson, and the processed lunch meat Spam. It's 40 years since the first Gay Pride march in London, and 25 years since Thatcher ratified the agreement to build the Channel tunnel.

So there's no excuse for the monomania we saw at the start of the year, when no one could have missed that 2012 is the 200th anniversary of Charles Dickens. The BBC began the year with a big Dickensian bang; the Museum of London has a special exhibition on until June, and Portsmouth has begun advertising itself as the place where Dickens was born. It's enough to make one wonder what will fill the airwaves and galleries this time next year. Or it would be, if I didn't know that 2013 is the 200th anniversary of Pride and Prejudice.