I HAVE a friend who is a fellow teacher at my school. She and I spend our days doing much the same thing - trying to get teenagers excited about the sine rule and the division of labour. She has four years' experience to my two, so she bails me out whenever I've forgotten to take the register or neglected to turn up for a detention I've set. At the weekend we sometimes do the same thing too: we go on dates with random men we have met online.

On Mondays, back in school, we compare notes, which usually means discussing the various ways in which the men will not quite do.

There is one difference between us. My friend is 25, while I am writing this article on the morning of my 60th birthday. My life at 60 is not what I was expecting - nor what the Mayor of London can have expected when he popped a 60-plus card into the post for me, allowing me to travel around London for nothing.

Evidently he thinks that having reached this age, I'm now too feeble and too impoverished to get from A to B unaided.

There is only one way in which life is going according to this plan. I am seeing a great deal of my dentist - which was always on the cards for my seventh decade as both parents had shocking teeth, and the apple (which I probably never ate in sufficient quantity) doesn't fall far from the tree.

Otherwise, life is everything it ought not to be. I am at the bottom of the career ladder, starting again professionally and, as it happens, romantically. Life is neither slow nor predictable.

The difficulty with this new phase is that we don't have the vocabulary for it. When I tell people I'm happy about this milestone they mostly reply with brave jocularity: "Life begins at 60!" or "60 is just a number!"

I'm not sure which annoys me most. Life does not begin at 60; by definition, it has been going on for an inordinately long time already. And the idea that 60 could be "just" a number not only offends the maths teacher in me but is plain wrong.

Not just a number

Sixty years is an exact measurement of how long I have been alive. Like everyone born in the UK in 1959, I can name Babs from Pan's People, I remember the excitement of the first Monty Python episodes, I did my homework by candlelight during the coal strikes, and I know how to address an envelope. These things are fundamental to the person that I am now.

The reason that people produce these dud aphorisms is they are frightened of being 60 and are vainly trying to make it sound better. The FT columnist Camilla Cavendish has just written a book that sets out to dispel these fears. Longevity, she argues in Extra Time, does not mean that old age becomes interminable, but that middle age lasts a lot longer than it used to.

Instead of measuring our age by how many years we have lived already, she suggests that we think in terms of how many we have left. This sounds banal but the shift in perspective is oddly profound.

Clearly, no one knows when they will die, but there are various life-expectancy calculators online to give us a clue.

Aviva's life assurance algorithm informs me that I will reach the age of 93, which means that I am now 33 years from death. This seems like a minor eternity, equal in length to the portion of life I lived between 27 and now.

That slice was large enough to contain a long marriage, four children, an entire, varied career in journalism and many important friendships.

The next 33 years will not contain any more children and may or may not contain a proper relationship, but they do leave room for another, extended, interesting career.

When Aviva asked for my likely retirement age I typed in 75 - but now I'm having second thoughts as that would still give me 18 years of retirement, which seems rather a lot.

Some gerontologists have started to subdivide old into "Young-Old", which runs from 60 to about 75 and bargains for activity, health and productivity, and "Old-Old", which bargains for none of the above.

Though I don't object to being classed as Young-Old, the phrase does not quite capture how I feel right now.

A better description would be Aged Adolescent: the recent appearance of liver spots on my hands reminds me that I'm aged, while my desire to push the boundaries of what it means to be my age was something I last did in a big way when I was 14. The only difference is that the risks that I'm now taking are not especially risky.

Risk and motivation

If I compare myself to my young friend, she is risking a lot with her career. She is at the beginning and has everything to prove - to herself and to others.

She needs to earn as much as possible as quickly as possible if she is ever going to get a foothold in the housing market. For her, the stakes are high. If she makes a mistake at school, it affects how she feels about herself - and how her bosses feel about her.

By contrast, I have little to prove. I have already been quite good at one thing and so my self-esteem is in decent condition. I know (more or less) who I am.

Above all, I have a pension, a house and children who are beginning to make their own way and parents who have moved beyond Old-Old. I don't need promotion, either for validation or for extra cash.

For the first time in my working life, I am only motivated by the job itself. I desperately want my students to love what I'm teaching, and I want to learn how to get better at my job. That's it.

I'm not trying to become the next principal of my school. If I screw something up, which I still do too often, I just think: oops, try not to fall into that trap again.

In this second-coming of a career, I am also making saner decisions about how I manage my time. Young teachers famously work themselves to a frazzle and within five years half of them have quit the profession for good. Because I'm in it for the long haul, I'm not going to let myself burn out.

The school day starts indecently early, and by about 5.30pm, when my brain starts to feel like a lump of putty, I down tools and go home. If my lessons are still only half-prepared, that's too bad - journalism has given me the ability to improvise.

The ageism of dating

So one way and another, I'm better placed at work than my 25-year-old friend. But what about dating? There, surely, the advantage runs the other way. She looks indisputably better than I do. She has smooth skin and shiny, bouncy hair. My skin shows every sign of having been around for six decades and my hair is grey. As a result of a car accident 45 years ago, I have a limp that is getting worse and I get the odd twinge of arthritis. The teeth, as I've mentioned, are not so good.

But never mind the outward signs, I'm happier about my appearance than I was in my 20s. My body may have sagged, but my expectations have sagged even more. I look at myself in the mirror with tolerance, and think: you look fine - for 60.

Alas, my male contemporaries on dating sites appear to feel less tolerance towards 60-somethings. In the job market, it is illegal to discriminate on the basis of age (although plenty goes on) but in the dating market, age discrimination is encouraged. On many sites, hopefuls are required to specify the age of their ideal partner: women of 60 typically say they are looking for a man within a five-to-10-year span of their own age in either direction, while men of my age routinely look for someone from 45 to 55 - or younger still.

As a result, most of my single female friends of 60 claim to be somewhere between 52 and 57 on dating sites. This might make sense, but strikes me as a minor catastrophe if the general aim is for everyone to stop being frightened of this age. Knocking off a few years is the worst possible way of dealing with ageism and cannot help anyone feel good about getting older.

Alas, the alternative isn't great either. From the outset, I faithfully typed my real birth date into the dating website, which means today my profile has updated itself and there is a big black 60 beside my photograph. Those two digits place me beyond the pale for about half of my male contemporaries.

Time to strike out

For me, it doesn't look good. I've just read a book by the pop-mathematician Bobby Seagull in which he calculates the probability of finding love in his mid-30s. The maths teacher's algorithm, which has coefficients for location, education, age and general fussiness, suggests that the probability of the next person on the pavement turning out to be his soulmate is one in 913,000. If I adjust the equation for age bias then for me it's about one in three million.

I'm refusing to let that dent my optimism. I am still in a better position than my 25-year-old friend because I'm not trying to meet a man to have children with, who will stay by my side for the next half a century.

The dating stakes for me are low, just as the career ones are, and the whole process is less painful. She reports that alcohol can be needed to get over the awkwardness of some of her dates, leaving her both disappointed and hungover afterwards.

For Young-Old dates, it's generally civilised conversation over coffee or a walk in a park. Expectations are modest, as is any disappointment that follows.

My young friend and I approach selection quite differently. She examines pictures carefully, vetoing anyone of unappealing appearance.

I examine prose, hunting for signs of intelligence, culture and humour - a sifting process that is less likely to lead to dismal dates. I only rule out a man purely on photo grounds if he has chosen (as a surprisingly large number of Young-Old men do) to display himself wearing Lycra on a bicycle.

The website tells me that in total I have read 233 profiles of men roughly my age, which leads me to conclude that many single 60-ish men are not finding it easy to be Young-Old. Some of them are already retired and are loudly claiming how much they adore travelling the world; all they need is a companion. I eliminate these on the grounds that they have made a bad life choice: pointless globe-trotting will surely pall over the next 33 years. An even larger number of them are drifting. They are semi-employed, doing a bit of this and a bit of that, and do not seem quite sure what to do next.

On dates with a couple of these, I have boldly suggested that they become teachers; with the comic result that my dating scorecard so far looks like this: Recruits to teaching 1; Soulmates 0.

Mr Seagull's advice to readers is to increase their chances by being open to new experiences and putting themselves out there. I don't need a mathematician to tell me that.

The greatest thing about being 60 is that there has never been a better time to strike out. No longer responsible for young children or ageing parents, this aged adolescent is up for most of the new experiences that life throws at her. FT

Lucy Kellaway is an FT contributing editor and co-founder of Now Teach, an organisation that helps experienced professionals retrain as teachers

Courtesy: The Business Times