Åk 6–9

2.1 Units and Concepts
There are many measurement units for time.  Some are more common than others.

Abbreviated s. Seconds are the standard unit (SI-unit) for time.
The SI-system come from the French "Système International d'Unités" and is an international standard for measurements and prefixes.

How long is a second really?  What can you do in a second? In 10 seconds?

We put a prefix in front of shorter time designations than a second.  For example, a millsecond (1 md) is a thousandth of a second (1/1,000 s) or one nanosecond (1 ns) is a millionth of a second (1/1,000,000,000 s).

Can you imagine how long a nanosecond is?

Abbreviated min. 1 minute = 60 seconds.

Quarter of an hour

A quarter = 15 minutes.

What can you do in a quarter of an hour?

In mathematics and physics, an hour is abbreviated as h.

1 hour = 60 minutes = 3,600 seconds.

Daylight is the time between sun up and sundown, the opposite of night.  The length of daylight varies depending on the season and where on Earth you are.

24 hours. It is the time it takes for the Earth to rotate around its own axis.

Leap day
An extra day which is added every fourth year because the Earth takes 365.25 days to rotate around the Sun.  It’s added as the 29th of February every fourth year.  The closest leap days will occur during the years 2008, 2012, 2016...

7 days. The start for a new week is Monday, and it ends on Sunday.  We have 52 full weeks in a year.

The number of days in a month varies between 28-31 days depending on the month. Every fourth year is a leap year and then we have 29 days in February instead of 28.   There are four weeks in a month.

You can use your knuckles to remember how many days there are in every month.

Foto: Fredrik Enander

Hold your hands next to each other.  Begin from the left with January.  Every knuckle represents 31 days and between the knuckles represents 30 days.  The exception is February which has 28 or 29 days.

Quarter of a Year
The year is divided up into quarters, in other words every quarter is 3 months.

1st Quarter: January, February and March

2nd Quarter: April, May and June

3nd Quarter: July, August and

4rd Quarter: October, November and

Comes from the Latin satio (time before) sowing, now the seasons or period during the year which return every year, like the winter season.  We also use the term in the sports world.  A season is a period when a sport (activity, game, series) is being played.


In Sweden, we have four seasons during the year: Spring, Summer, Fall and Winter.  This is because Sweden is a country that covers 160 Swedish Miles (1,600 km) in a north-south fashion.

A simple picture of how the seasons are divided up during the year, you can see to the right.

Academic Year
An academic year in Sweden’s schools is 185 work days.  It begins in August and ends in June the following calendar year.  Every county in Sweden determines the exact date for the start and end of the school year.

The time it takes for the Earth to complete a revolution around the Sun. 365.25 days.

Leap Year
Because it takes the Earth 365.25 days to complete a revolution around the Sun, every fourth year has an extra day (29th of February).  A year which has this day, the leap day, is called a leap year.

Calendar Year
1 January – 31 December

A period which contains 10 years. For example 1954 – 1964. We often mean even 10 year periods. For example 1980-1989 or 1990-1999.

A period containing 100 years.  For example 1880 – 1980.  We often refer to an even 100 years.  For example 1700’s (1700-1799).

A period containing 1,000 years. For example 560 -1560. We often refer to an even 1,000 year period.  For example 1000 (from year 1000 to 1999) and 2000 (year 2000 to 2999). We live in the 2000’s.