This is a widget for Apple Computer's Dashboard feature of Mac OS X version 10.4 (Tiger). It calculates the time of sunrise and sunset based on the date and your location.
Download the latest version. (version 0.2 (beta))
The algorithm was borrowed from a NOAA Surface Radiation Research Branch's web page, called the NOAA Improved Sunrise/Sunset Calculation and has the same strengths and weaknesses. (Though the widget probably has a few more bugs.)
For latitudes greater than 72 degrees N and S, calculations are accurate to within 10 minutes. For latitudes less than +/- 72° accuracy is approximately one minute. The widget will not allow you to enter latitudes greater that 89.8°. The widget might still be buggy -- use at your own risk.
The first thing you need to do after installing the widget is to tell it where you are. Flip it over (place your mouse pointer over the widget and click on the "i" that appears in the lower right corner) and look at the preferences.
First note the "Presets" menu that lists a lot of cities. If you live in one of cities, choose it. Otherwise, choose one that you live near, if you can. Then, if necessary, you can enter a better latitude and longitude for your position.
Note that the latitude and longitude are in "degrees", "minutes" (of arc), "seconds" (of arc), and "hemisphere" ("N", "S", "W", or "E"). Simply enter your numbers in the boxes, and click the hemisphere button if you need to change it. If you know your latitude and longitude in decimal form (E.g., 47.60, 122.3167) you can just enter those in the "degree" boxes and the widget will convert it for you. The rule is: If the degrees has a decimal point, it will fill in the other bits.
The "Time Zone" box is the offset (in hours) of your standard time zone (not daylight savings) from UTC (formerly known as Greenwich Mean Time.) For example, "Pacific Standard Time" would be "8" and "India Time Zone" would be "-5.5". Then you can check the "Daylight Savings" box as appropriate, which will shift the effective time zone by an hour. (E.g., A "Time Zone" of "8" with "Daylight Savings" turned on is equivalent to a "Time Zone" of "7" with "Daylight Savings" turned off.)
Warning: The widget does not know when daylight savings time (if any) starts or stops for where ever you happen to have set the widget to. When you set your clocks forward or back, you will have change the widget by hand.
By default, the widget shows you the sun's rise and set times for the current day.
You can look a few days into the future or past by clicking on the arrows, or return to the present by clicking on the spot between the arrows.
Allow for the entering of random dates.
Allow the time zone to be entered as "-800".
You may contact the author at 
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Last modified on October 29, 2005 about three hours before sunset.