In July 1962 – in what could be seen, with hindsight, as a pre-emptive up-yours to the entire career of David Blaine – a French explorer named Michel Siffre buried himself under a glacier for two months. More than 100m below ground, several degrees below freezing and confined to a tent in a cave, the 23-year-old's sense of time soon unravelled. Deprived of the markers with which the rest of us keep track – clocks, sunrise and sunset, weekdays and weekends, birthdays, seasons, term times, holidays – he grew disoriented. Hours seemed to pass in seconds, then minutes would stretch into hours; sometimes, most confusingly, both would seem to happen at once. A few weeks in, he was shocked to receive a message from the surface, summoning him back to civilisation a month early. Except it wasn't a month early. It was September: two months had passed in what felt like 34 days.

You couldn't ask for a more vivid reminder of how badly we need "temporal landmarks" to give life structure, and keep us sane. And those landmarks exert subtle influences on us. One new study, in the Journal of Consumer Research, found that people were more likely to meet a six-month deadline if given it in June, with an endpoint in December, than in July and ending in January. The new year serves as a divider: we define the stretch of time before it as similar to the present, and deadlines occurring within it as more urgent; the other side of new year, by contrast, seems like a far-off land. Then again, this is social psychology, so of course there are studies suggesting the precise opposite: that you should schedule major deadlines for just after milestones such as holidays or birthdays. The theory goes that this will increase the sense of contrast between your present self (who hasn't yet met the goal) and your future self (who has), thereby focusing the mind and providing a motivational boost.

Which method works for you may depend on whether you find big challenges energising or paralysing. But in any case, both findings point to a more general truth: temporal landmarks really matter. Build more of them into your life – or pay more attention to existing ones – and you'll experience time differently than if your days and years are one undifferentiated mush. Besides, for anyone over about 30, there's another reason to care: temporal landmarks could help assuage that terrible feeling of time speeding up as you age. In what researchers call the "calendar effect", we use milestones to form and retain memories – so university students, say, have much better recall of events near the start or end of term, even when you allow for the emotional highs and lows of freshers' week or graduation. The more landmarks, the less risk of suddenly realising you've no idea where last year went.

All of which is an excellent argument for making sure you celebrate birthdays; for holding a proper leaving do next time you leave a job or a city, instead of slinking off; for celebrating Christmas even if you're an atheist; maybe even for grand weddings over modest ones. Sadly, you needn't bury yourself beneath a glacier to have that sense of a month having simply vanished: a life without landmarks may suffice.

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