Far back in the mists of time, people must have got fed up with everyone being late for everything. Someone came up with the bright idea of time and how to measure it.

Second Nature. The most obvious way of measuring time is, of course, the Sun coming up, going down and then coming up again: a day. People probably caught on to that one fairly fast. And the Moon goes through phases, from a sliver to a circle, of about a month, which divides time into bigger chunks.

The Ancient Egyptians came up with the 365-day calendar. They’d noticed that some things happened once every twelve months, like the flooding of the River Nile. The earliest recorded year was 4236 BC.

If you want to be a bit more specific, you need to divide up the day into smaller chunks. The ancient Babylonians came up with 60 seconds in a minute, 60 minutes in an hour and 24 hours in a day. Ever since then, people have been inventing time-measuring devices: clocks.

1 year is equal to 12 months • 52 weeks • 365 days • 8,760 hours 525.600 minutes • 31,536,000 seconds

10 years is equal to 1 decade • 120 months 520 weeks • 3,650 days • 87,600 hours • 5,256.000 minutes • 315,360.000 seconds

100 years is equal to: 1 century • 10 decades • 1,200 months • 5,200 weeks • 36,500 days • 876,000 hours • 52,560,000 minutes • 3.153,600,000 seconds

BUT these sums don’t include leap years. A leap year consists of 366 days instead of 365. This extra day is added to February every four years, giving the month 29 days instead of 28.

The last 10 leap years were in: 1972, 1776, 1980, 1984, 1988, 1992. 1996, 2000. 2004 & 2008

The next 10 leap years are in: 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044 & 2048

So for every four years that you’ve been alive, add 1 day • 24 hours • t.440 minutes • 86,400 seconds

AND if that isn’t enough to think about there are also leap seconds! Believe it or not but some years are longer than others! Every now and again scientists add an extra second to the year (and sometimes two in a year). There have been 23 leap seconds in the last 35 years. The last leap second to be added was to the end of 31 December 2005, making the time 23:59.60 – so bung a few extra seconds on to your answers for good measure!

Sundials were used to measure time over 5,000 years ago. Water clocks, which drip water at a constant rate, told the time in Egypt and Babylon around 3,500 years ago.

Dutch scientist Chrishaan Huygens invented the first mechanical pendulum clock in 1656. In the 20th century mechanical clocks were replaced by quartz-crystal clocks, in which crystals vibrate at a constant rate.

Atomic clocks use the resonance of atoms to measure time. The first accurate one was built by Louis Essen in 1955. But not many people need to be that precise.

Lunar-ticks: Sticks and bones with lines and holes scratched into them dating from 20,000 years ago are thought to be Ice-Age Moon calendars. Notches carved into the sticks are thought to represent days between each phase of the Moon.