Sunrise & Sunset Times for 2014

 

Did you know that the shortest day is not necessarily the day of the latest sunrise? Did you know that the latest sunrise and the earliest sunset do not occur on the same date? Did you know that the longest day isn’t the same day as the earliest sunrise and the latest sunset? Are you lost when someone asks when the summer solstice is, or when the equinoxes occur?


Click this link: SunTime for the sunrise and sunset times for 2014.  This will take you to an external site as I have decided that there are too many sites out there already which display the same information. Furthermore, you may not be in Sheffield, UK and so you may wish to customise the data for your own location, which you can do if you follow the link.


The days of the earliest sunset, latest sunrise and least number of daylight hours are highlighted in black. The days with the earliest sunrise, latest sunset and greatest number of daylight hours are highlighted yellow.


The days on which the clocks change are indicated in text format.


The winter solstice always falls on December 21st and the summer solstice always on June 21st. The Spring Equinox is always on March 21st and the Autumn Equinox is always on September 21st. These dates also mark the changing of the seasons, with Winter starting on December 21st, Spring on March 21st, Summer on June 21st and Autumn on September 21st.


Some useful definitions for anyone new to the different types of twilight, measurements of illumination and sun position:

Civil Twilight
Civil twilight occurs when the centre of the sun is between 0 & 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.

(Photograph location: Ben Hope, Scotland, from the website of Lesley Punton.)

Nautical Twilight
Nautical twilight is defined when the sun is between 6 &12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct.





(Photograph location: New York, USA, from the website of Ashley Fetner.)

Astronomical Twilight
Astronomical twilight is defined when the centre of the sun is between 12 &18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the sun does not contribute to sky illumination; for a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible.




(Photograph location: High Bradfield, Nr. Sheffield, from website of Robin Jackson.)

Solar Noon
Solar noon is the time when the sun reaches the highest point in the sky at the location from where you are measuring the time and height.

Twilights and dusks
The diagram to the right shows the position of the centre of the sun in relation to the horizon at Sunset, the three twilights (see above) and the three dusks (which occur as the sun makes the transition from one twilight to the next or from Astronomical Twilight to night).


If you replace the word “dusk” with “dawn”, replace “sunset” with “sunrise”, and ‘read’ the diagram from the bottom up, you can see the transitions for daybreak rather than sundown.

Lighting Up time
Lighting-Up time - 30 minutes after sunset until 30 minutes before sunrise - refers to the time during which vehicles must use their headlights, and dates back to the 1800’s when regulations were introduced requiring horse drawn carriages & bicycles to display lights. These by-laws were combined into the Lights on Vehicles act of 1907 and revised in 1942, when the Road Lighting Act dictated that lights must be displayed on road vehicles from an hour after sunset until an hour before dawn. A later revision in 1956 reduced the times to 30 minutes because of the increasing speed of motor vehicles. The 1989 revision of the law additionally made it a legal requirement that all vehicles display “conspicuity” (side, tail & number plate) lights between sunset and sunrise.

Street & Amenity Lighting

Contrary to popular belief, Lighting Up Time does not refer to street lighting, although street lamps on pilot mains (which are only just being phased out in Sheffield) generally had their time-switches, set to closely match lighting up time (often using Sangamo Weston Solar Dial switches, which leave the factory set to operate at lighting up times for the specified latitude and longitude). Modern, photocell switched, street lamps will automatically switch on and off when the light levels match Civil sunset and sunrise in clear weather conditions ... or at least they will if they are correctly installed, properly oriented towards north .... which they rarely are, hence the very unusual switching of street lighting often observed!

Sunrise & Sunset as a graph

Here you can see a graphical representation of the changing times of sunrise and sunset (with strange “bumps” where the clocks change) and the equinoxial dates indicated by marker lines. Very close inspection will allow you to see that the solstices do not have the earliest / latest sunrises / sunsets. (Note the graph is not for the current year but the pattern is the same each year.) Red line is sunrise; blue line, sunset.

Azimuth

The azimuth displayed on the sunset / sunrise page is the horizontal direction of the Sun at sunrise or sunset at the times displayed in the Sunrise and Sunset columns. As on a compass, the azimuth is measured in degrees, with 360 in a full circle, counted in a clockwise direction from north. North has an azimuth value of 0 degrees, East is 90 degrees, South 180, etc.

It is important to note that the directions refer to true north and not to magnetic north. True north being north according to the Earth’s axis, whilst magnetic north is the direction in which the north end of a compass needle will point in response to the Earth’s magnetic field.