Patent Publication Number: US-7218575-B2

Title: Angular twilight clock

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention relates to a method for displaying time. More specifically, the subject invention relates to a method for displaying time at a particular coordinate position on the earth. 
   2. Description of the Prior Art 
   It is often desirable to know the commencement of light, darkness and the twilight. This need is often complicated when travelling between time zones. Prior clock systems provide clocks that indicate times for sunrise, sunset and twilight. One such clock system is described in the U.S. Pat. No. 4,669,891 to the inventor herein, Rosevear. The prior Rosevear &#39;891 patent discloses a keyboard for inputting an area code or an airport designation for a geographical location. A memory contains information of the sunrise, the sunset time and the twilight duration for each area code or airport designation that can be selected. A microprocessor generates a signal, based on information gathered from the memory, which corresponds to either the input area code or the input airport designation. The signal is then presented on a video display screen in parallel vertical sections that represent juxtaposed hours of the day for the selected geographical location that includes each of the day, night and twilight hours. 
   Another clock system is described in the U.S. Pat. No. 6,449,219 to Hepp et al. (the &#39;219 patent). The &#39;219 patent provides an analog clock that is contained within a time sensing information display device. The display device contains a rectangular display area. On the display area is a graphical depiction of a tree with a round treetop, a horizon and a sky. The analog clock is incorporated within the round treetop. As the time of day changes, the sky alters to show a sun or a moon that is either waxing or waning. Furthermore, the display device incorporates a global positioning receiver which allows the proper display of the time, the sun and the moon based on the display devices&#39; geographical location. 
   Although the prior art clock systems provide a visual display of day, night and twilight hours or a visual display of the sun and moon based on a geographical location, derived from a global positioning system, there remains an opportunity for a visual clock system which provides a more instantly understandable method of displaying the day, night and twilight hours based on geographical coordinates and a calendar date. 
   SUMMARY OF THE INVENTION AND ADVANTAGES 
   The invention provides a method and apparatus for displaying time including storing a day sequence that includes times for the beginning and ending of twilight and sunrise and sunset for each calendar day of the year for various coordinate positions in a memory. A stored day sequence is retrieved from the memory that corresponds to a registered current coordinate position and current calendar day. The final step includes presenting the current time on a circular clock face with pie-shaped sections for twilight. 
   Accordingly, an improved visual display of pie-shaped twilight hours, based on a coordinate position and calendar date, is established. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein: 
       FIG. 1  is a diagram illustrating an apparatus for displaying time; 
       FIG. 2  is a block diagram illustrating a method for displaying time; 
       FIG. 3  is a example of the display of time generated by the method; 
       FIG. 4  is another example of the display of time generated by the method. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 and 2 , a method and apparatus for displaying time are generally shown at  10 . Those skilled in the art will appreciate that the term “twilight conditions” used herein refers to the time for twilight, sunrise and sunset. Twilight is the soft, diffused light from the sky when the sun is ante meridian or post meridian below the horizon. Twilight occurs either from daybreak to sunrise or from sunset to darkness. There are three scientifically recognized types of twilight: civil, nautical and astronomical. Each is defined by how the distance or angle of the sun&#39;s center below the horizon. Civil twilight is when the sun&#39;s center is six degrees (6°) below the horizon; nautical twilight is when the sun&#39;s center is twelve degrees (12°) below the horizon; and astronomical twilight is when the sun&#39;s center is eighteen degrees (18°) below the horizon. Twilight conditions vary based on the geographical location and the calendar date. The method described herein displays time on an analog clock face  36  with pie-shaped sections for the twilight conditions  22 . The analog clock face  36  is preferably circular and can be presented on a variety of electronic devices with a memory  12  and a register  16 . These devices can be a personal data assistant (PDA), a personal computer, a desk clock, a wall clock, or even a wrist watch. However, those skilled in the art will realize that other devices can be utilized so long as they employ the necessary memory and registering capability. 
   A memory  12  stores a day sequence that includes times for the beginning and ending of twilight, sunrise and sunset for each calendar day of the year for various coordinate positions. A receiver  14  receives a current coordinate position in latitude and longitude, a current calendar day and a current time. A register  16  is operatively connected to the memory  12  and the receiver  14 . 
   First, the receiver  14  receives a current coordinate position in latitude and longitude, a current calendar day and a current time. In the preferred embodiment, the receiver  14  is a global positioning receiver  14 . The global positioning receiver  14  receives information pertaining to a current coordinate position in latitude and longitude, a corresponding current calendar day, and a current time by receiving a global positioning signal and determining the current calendar day, the current time, and the current coordinate position. Additional types of receivers  14  can also be a Long range navigation (LORAN) receiver, a radio, or a cell phone. However, the receiver  14  can also establish a location by being a manual input device  14 . In this embodiment, registering a current coordinate position in latitude and longitude, a current date and a current time results from manually inputting the coordinate position in latitude and longitude, the current calendar date and the current time into the receiver  14 . One skilled in the art can appreciate that inputting the information manually would be helpful when the user is curious about the twilight conditions for various geographical locations at varying dates and times. Alternatively, receiving this information can come from manually inputting the coordinate position in latitude and longitude and then receiving the corresponding calendar date and corresponding time from the atomic clock. In yet another embodiment, receiving this information comes from the user choosing a city, a calendar date and a time from a pull-down menu on the electronic device. 
   Next, the register  16  registers the current coordinate position in latitude and longitude, the current calendar day and the current time from the receiver  14 . The register  16 , takes this registered information and retrieves  18  a stored day sequence from the memory  12  that corresponds to the registered coordinate position and current calendar date and presents the current time on a display device  20 . The stored day sequence is preferably calculated through a series of algorithms based on the current coordinate position, the current day and the current time. However, the stored day sequence can be based on discrete coordinated positions. 
   A display  20  is operatively connected to the register  16  and the memory  12 . The display  20  presents the current time on a circular clock face  36  with pie-shaped sections for twilight  22 . 
   The pie-shaped sections for twilight  22  have a first and a second boundary  28 ,  30  that define the duration of civil, nautical or astronomical twilight. The first and second boundary  28 ,  30  of the pie-shaped section for twilight  22 , in the clockwise direction, depends on whether the previous section  24  corresponds to either night or day. If the previous section  24  corresponds to night, then the first boundary  28  represents the start of the twilight time and the second boundary  30  represents the sunrise time. If the previous section  24  corresponds to day, then the first boundary  28  represents the sunset time and the second boundary  30  represents the end of twilight. Furthermore, the time duration between the first  28  and second  30  boundaries represents the duration for twilight. Twilight time can be civil, nautical or astronomical. In the preferred embodiment, the twilight time presented represents nautical twilight. In an alternative embodiment, any, or all, of civil, nautical and astronomical twilight time can be presented in these pie-shaped sections for twilight  22  at one time. 
   Additionally, the display includes pie-shaped sections for day and night  22 ,  24  respectively. The first boundary  32  for the day pie-shaped section  24 , in the clockwise direction, represents the sunrise time. The second boundary  34  for the day pie-shaped section  24  represents sunset. For the night pie-shaped section  24 , the first boundary  32  represents the end of night time twilight. The second boundary  34  of the night pied shaped section  24  represents the beginning of the day time twilight. Therefore, the time duration between the first  32  and second  34  boundaries of either the day or the night pie-shaped sections  24  represents the duration for either day or night respectively. 
   In the preferred embodiment, the time is presented on a twelve hour analog clock face  36 . Examples of the preferred embodiment are shown in  FIGS. 3 and 4 . The pie-shaped sections for twilight  22  and either day or night  24 , represent the twilight conditions for the successive twelve hours. The pie-shaped sections  22 ,  24  are differentiated by being different shades or colors. In the present invention, blue represents day, black represents night, and gray represents twilight. However, other colors can also be employed to satisfy individual preferences. As time progresses, the pie-shaped sections  22 ,  24  are repositioned at predetermined times  26  to reflect the successive twelve hours. Preferably, the predetermined times are noon and midnight respectively. 
   In an alternate embodiment, the time is presented on a twenty-four hour analog clock face  36 . The pie-shaped sections for twilight, day and night  22 ,  24  represent the twilight conditions for the successive twenty four hours. As time progresses, the pie-shaped sections  22 ,  24  are repositioned  26  at a predetermined time to reflect the commencement of twilight, sunrise and sunset for the successive twenty-four hours. Preferably, the predetermined time for repositioning  26  the pie-shaped sections  22 ,  24  is midnight. In another embodiment, the pie-shaped sections  22 ,  24  are repositioned  26  continuously. Continuously can be every second, minute, hour or any arbitrary amount of time. With continuous repositioning  26  of the pie-shaped sections  22 ,  24 , the clock face  36  represents the twilight conditions for the successive twelve hours, if using a twelve hour analog clock  36 , or the successive twenty-four hours, if using a twenty-four hour analog clock  36 . In yet another embodiment, the pie-shaped sections  22 ,  24  are repositioned  26  when the user manually requests an update to the display  20 . This can be accomplished, for example, by pressing a button on the electronic device or by using a keyboard. 
   Those skilled in the art will appreciate additional times for repositioning  26  the pie-shaped sections  22 ,  24  may also be needed. For example, when the electronic device is moved to a new coordinate position, or if daylight saving time needs to be accounted for on the clock face  36 . The device may automatically account for these by adjusting the time and repositioning  26  the pie-shaped sections  22 ,  24 . 
   To provide the user with additional information, other embodiments of the invention can provide time and geographical information approximate the clock face  36 . The information displayed can include the current calendar date, the current time zone, the current coordinate position in latitude and longitude, the current time digitally, and the times for twilight, sunrise and sunset. 
   Obviously, many modifications and variations of the present invention are possible in light of the above teachings.