If it feels like all you did was blink at New Year’s and now here we are in August, you'll probably be contemplating why time feels like it goes by at lightning speed the older you get.
Summer holidays used to be so long when you were at school, but if you were given six weeks off work now - it would pass in a flash.
But it turns out you're not just imagining it. There are some actual, scientific theories as to why we perceive time to go much faster as we get older, and Dr Christian ‘Kit’ Yates, a lecturer in mathematical biology at the University of Bath, wrote all about them in an article on The Conversation.
The biological reason
"The theory goes that the older we get, the more familiar we become with our surroundings. We don’t notice the detailed environments of our homes and workplaces," Dr Yates explained.
Because, to children, the world is still new and generally unfamiliar, they use more brain power to consume what's around them. "The theory suggests that this appears to make time run more slowly for children than for adults stuck in a routine," the lecturer wrote.
This theory is also backed up by biology. It's thought that the more a person is stimulated by their surroundings (ie, not familiar with their everyday routine as we become when we're adults), they release the 'happy hormone' dopamine. When we reach the age of 20, dopamine levels begin to drop, and continue to do so as we age, which also contributes to time being perceived as moving faster.
The mathematical reason
There's one other theory that may explain why time appears to speed by the older we get, and it's all about percentages. "The idea is that we perceive a period of time as the proportion of time we have already lived through," explained Dr Yates.
He went on to use the example of a toddler. "To a two-year-old, a year is half of their life, which is why it seems such an extraordinary long period of time to wait between birthdays when you are young.
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"To a ten-year-old, a year is only 10 percent of their life, (making for a slightly more tolerable wait)," the expert continued. "To a 20-year-old it is only percent."
"For a 20-year-old to experience the same proportional increase in age that a two-year-old experiences between birthdays [ie, half their life], they would have to wait until they turned 30. Given this view point it’s not surprising that time appears to accelerate as we grow older," he summarised.
Dr Yates used this notion to end on something of a philosophical point. "The five-year period you experienced between the ages of five and ten could feel just as long as the period between the ages of 40 and 80," he wrote.
And when you think about it like that, you realise how short life really can be. So let's make sure we make the most of it.
Read Dr Yates' full article over on The Conversation.