Solstices and equinoxes
The longest day, the shortest day, and two equal days.
Long days, short days
Days are longer in summer and shorter in winter. In between, one day of the year is the longest.
Around which date do you think the Northern Hemisphere has its longest day?
What this lesson covers
The idea
In the Northern Hemisphere the longest day, around 21 June, is the summer solstice and the shortest day, around 22 December, the winter solstice; around 21 March and 23 September, the spring and autumn equinoxes, daytime lasts 12 hours.
Long days, short days
Days are longer in summer and shorter in winter. In between, one day of the year is the longest.
Around which date do you think the Northern Hemisphere has its longest day?
- 21 June
- 21 March
- 22 December
Four dates
Tap each date on the orbit. The red line is the axis.
Now see how much of a circle of latitude is in sunlight on each date.
Two solstices, two equinoxes
The longest and the shortest days are the solstices. The two days with equal day and night are the equinoxes.
In the Northern Hemisphere the longest day, around 21 June, is the summer solstice and the shortest day, around 22 December, the winter solstice; around 21 March and 23 September, the spring and autumn equinoxes, daytime lasts 12 hours.
- Date | Name | Daytime in the Northern Hemisphere
- Around 21 June | Summer solstice | Longest day
- Around 22 December | Winter solstice | Shortest day
- Around 21 March | Spring equinox | 12 hours
- Around 23 September | Autumn equinox | 12 hours
Notes
In the Northern Hemisphere the longest day, around 21 June, is the summer solstice and the shortest day, around 22 December, the winter solstice; around 21 March and 23 September, the spring and autumn equinoxes, daytime lasts 12 hours.
Check yourself
The longest day in the Northern Hemisphere is around …
The shortest day in the Northern Hemisphere is called the …
How many hours does daytime last on an equinox?
Answer: 12 hours
12 hours.
Which two dates are the equinoxes?
- 21 March. Daytime is 12 hours around 21 March.
- 22 December. That is the shortest day.
- 21 June — correct. Yes! This is the summer solstice.
- winter solstice — correct. Yes! It is around 22 December.
- summer solstice. The summer solstice is the longest day.
- autumn equinox. On the equinoxes, daytime lasts 12 hours.
- 21 March and 21 June. 21 June is a solstice, not an equinox.
- 21 June and 22 December. Those are the two solstices.
- 21 March and 23 September — correct. Yes! Day and night are equal on both.