Now that we are in the month of March, for most of us in the northern hemisphere the worst of the winter is over, and it is only a couple of weeks until 21 March, the first day of spring. 21 March is an important date for other reasons, too. For one thing, it is used as the basis for the… Continue reading The first day of spring
Category: Time
The evenings are drawing out already
Revised 14 December 2025 As I complete this post, it's completely dark outside and it's only 5 o'clock in the afternoon. Today is 14 December, and most people I come across think that it will continue to get dark earlier and earlier in the afternoons until 21 December (the date of the winter solstice in 2025), the… Continue reading The evenings are drawing out already
How the length of a day changes over the year
The length of a solar day varies throughout the year, ranging from about 23 hours 59 minutes 38 seconds in mid-September to 24 hours 30 seconds around Christmas. This variation is caused by the Earth's elliptical orbit and axial tilt, affecting the Sun's apparent motion and leading to differences in natural time measured by sundials versus clock time.
The June Solstice
The June solstice, which for most of the world will fall on June 21 this year, is the longest day in the northern hemisphere and the day when the Sun is at its highest in the midday sky (see note). The origin of the word solstice is from the Latin words sol, which means Sun, and sistere, to stand… Continue reading The June Solstice
Jun 30 2015 – Leap Second
On June 30 2015 an extra second will be inserted into the very end of the day. This extra second is called a leap second. Why do we need leap seconds? Although we take the average length of a day to be 24 hours, the mean solar day, or average "natural" day measured by the… Continue reading Jun 30 2015 – Leap Second
Explaining Science 