• Why do I sometimes see the Sunrise or Sunset before/after the calendar says it should occur?

    Due to the bending of the sunlight as it passes through the Earth’s atmosphere, it is possible to see the Sun before/after it has actually crossed the horizon. As the degree to which the atmosphere bends sunlight is highly dependent on weather, it is impossible to predict the exact time sunrise and sunset will be observed throughout the year. It is standard practice, however, to assume a refraction angle of 0.6°. If your calendar was made for a location far from the equator, slight differences in the refraction angle can significantly shift the observed timing of sunrise and sunset due to the low angle the Sun’s path makes with respect to the horizon. 

  • How does my location build my Calendar?

    Staring from the latitude, longitude, and time zone information you fill out when ordering your calendar, I compute the time of sunrise, sunset, local solar noon, moonrise, moonset, and the transitions between twilight periods for each day of the year. This data, in addition to calculations about the phase of the Moon, generates the calendar as explained in the Design section of this site. In general, within a time zone, motions north or south affect the durations of daylight, twilight, darkness, and moonlight. Movement east or west will affect the rotation of the daylight diagrams as explained in the Science section of this site.


  • Why is everthing described in terms of latitude and longitude instead of miles or kilometers?

    All of the variations possible in the Yearlight Calendar are based on latitude and longitude, not physical distance, because the Earth’s surface is roughly spherical. Near the poles, where longitude lines converge, movements of a few miles (kilometers) east or west can alter your longitude dramatically, where as the same movements at the Equator will barely have an effect on your longitude. For this reason it is only possible to make general statements about how longitudinal shifts, not distances, affect the timing of celestial events.

    If you would like to calculate how distances at your latitude translate into longitudinal shifts you can use the following equation:

    a = 180*d/[20015*cos(L)]


    a = the change in longitude

    d = the distance moved east or west (measured in kilometers)

    L = your latitude (measured in degrees)

  • What do characters like “ and ‘ mean when measuring angles?

    When measuring angles, the apostrophe (‘) is used as a symbol for arc-minutes, 1/60th of a degree. The quotation mark (“) is used to indicate arc-seconds, 1/60th of an arc-minute.


  • What are “minutes” and “seconds” when referring to angles?

    When measuring angles it is common to divide each degree (°) into 60’ (arc-minutes) equal to 0.01667°. Each arc-minute is divided into 60” (arc-seconds) equal to 0.00028°. Thus, a precise measurement of an angle can be given in terms of the number of degrees, arc-minutes, arc-seconds, and, via decimals, fractions of an arc-second.

  • What is the correlation between longitudinal displacement and the shifting time of celestial events?

    In general, movements east cause phenomena such as sunrise and sunset to occur earlier, while movements west cause these phenomena to occur later in the day, according to local Standard Time.


    Displacements of 15° to the east/west result in events occurring 1 hour earlier/later. (±15° = ±1 hr)

    Displacements of 1° to the east/west result in events occurring 4 minutes earlier/later. (±1° = ±4 min)

    Displacements of 15' to the east/west result in events occurring  1 minutes earlier/later. (±15’ = ±1 min)

    Displacements of 1' to the east/west result in events occurring 4 seconds earlier/later. (±1’ = ±4 sec)

    Displacements of 15” to the east/west result in events occurring 1 seconds earlier/later. (±15” = ±1 sec)

    Displacements of 1” to the east/west result in events occurring 0.25 seconds earlier/later. (±1” = ±0.25 sec)


    If a time zone boundary is crossed during an angular displacement, these calculations will not correspond to the timing of the events as measured by Standard Time.


  • Are mountains, buildings, and other objects that obstruct my horizon taken into account in the Yearlight Calendar?

    No. The calculations are with respect to your “true horizon”: the horizon at your location assuming no obstructions, and an altitude of 0 ft (m).

  • Who came up with the Yearlight Calendar?

    The Yearlight Calendar was designed by Bradley Pitts, an artist who explores the space between personal experience and objective measures. For more information on Bradley’s other work please see his website at www.bradleypitts.net.

  • Where does the name “Yearlight” come from?

    The name Yearlight was chosen to convey the changing light throughout the year. Just as “daylight” means “the light of day”, “yearlight” was coined to mean the light of a year.


  • What was the motivation for the Yearlight Calendar?

    Like much of Bradley Pitts’ work, the Yearlight Calendar explores the relationship between personal experience and rational, pragmatic methods. These methods are usually built on a standard system of measurement and quantification. Time is no different.


    From pole to pole Standard Time imposes a fixed measure of time insuring that 12:00 PM (or any other hour) occurs at the same moment for everyone within a given time zone. None of these people, however, will observe exactly the same timing of celestial phenomena such as sunrise, sunset, and local solar noon. The institutionalized, standard measure of time neglects the natural, site-specific details that make our experience of day and night so profound. 


    The Yearlight Calendar was designed as a way to honor the dynamic, local experience of time throughout the year while still providing the practical aspects of a standard calendar. 


  • What is the difference between “site-specific” and “horizon-specific”?

    All horizon-specific phenomena are site-specific because the horizon forms a circle centered below one’s exact latitude and longitude. It therefore travels with you. Because no two people can occupy the same space at the same time their horizons are always slightly different. The Yearlight Calendar is horizon-specific because all of the events depicted by it, such as sunrise, occur with respect to the horizon. 

  • What goes into the calculations behind the Yearlight Calendar?

    Accurately predicting the timing of sunrise, sunset, and all the other phenomena depicted on the Yearlight Calendar is much more complicated than you might imagine. It is certainly more involved than we first expected. This is because the gravitational effects of the Earth, Moon, Sun, Venus, Mars, and Jupiter affect one another, introducing small disturbances in their motions, which must be taken into account. It is possible to simplify these equations by making approximations, but this obscures some of the truly unique horizon-specific timing of celestial events. For this reason we decided to use more accurate, and far more complicated algorithms for the calculations behind the Yearlight Calendar. 


    In addition, in order to create the most robust calculations, valid for the entire Earth’s surface, we decided to calculate the Sun and Moon’s position for every minute of every day. We appreciate knowing that the data is as accurate and robust as contemporary, self-contained algorithms allow and hope you will too!

  • What’s with the color scheme?

    The look of the Yearlight Calendar was intended to be highly geometrical and somewhat Modernist. For this reason it uses primary colors, but instead of using the Modern era’s primaries (yellow, red, and blue), it uses contemporary primaries: Cyan, Magenta, Yellow, and Black (CMYK). These are the foundational colors of contemporary printing processes and are used in the calendar to register the fundamental experience of time, driven by celestial phenomena. 

  • What is special about the limited edition prints?

    The limited edition prints are more precise to your location because they are specific to your address instead of just your city. They can even be made specific to a room within your house. Even though 100 people can order these prints, no two will be exactly alike. 


    In addition, the blacks of the limited edition prints are deeper because they are printed by layering all the CMYK colors on top of one another. This is called “registration black”. 


    Finally, the prints are produced on 100% archival rag paper and signed by Bradley Pitts, the designer of the Yearlight Calendar.


  • Who did the programming for the Yearlight Calendar?

    Timothy (a.k.a. “Tims”) Gardner. Early prototyping was performed by Keith (a.k.a. “Keiths”) Hartwig.