A unit of Lasting Forests evolving since March 30, 1999
A Total Forest Management Plan and Wildland Management Decision Support System
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Day-Length and Hours of Light

Day length is the number of hours from sunrise to sunset.

First is presented the total hours of daylight for your area, monthly, during the growing season, and annually.

Summary Table - Daylight for the Area
Monthly Totals January February March April May June July August September October November December Growing Season Total Annual Total Light	x x x x x x x x x x x x xxx 4285.48

Only the main heading and the top line for a 21-page single-spaced table is given. (Based on early CAPs work and a USFS computer program)

Daylight becomes a resource for workers, for recreationists. It is a measure of the potential for an area to fix energy (in which photosynthesis may be active). Relative amounts of daylight will surely be a controlling variable in ecosystem studies. Day length is the period within which legal hunts and fishing may occur. Many crop plants require a specific number of hours of light to mature fruit. It relates to things that can be seen in law enforcement cases as well as wildlife observation. A program will show "dawn" 1 hour before daylight and "dusk", one-hour after sunset. See also the residual, the night period.

The following table shows the hours of light throughout the year for the area. This table is unique for your latitude (obtained from using a GPS in the field). The Julian day (January1- day 1) is shown first, then eastern standard time (EST) for sunrise and sunset, then twilight.

Daylight							Twilight
Julian Day	Standard Date		Sunrise		Sunset		Morning		Evening		Day Length Hours
	Month	Day	EST	DST	EST	DST	EST	DST	EST	DST
1	Jan	1	754	854	1709	1809	726	826	1736	1836	9.55

Note that 9.55 = (1709-754)/100

9.55 x 365 days = 3485.75 or approximate total light.

Degree Days

Temperature degree days are estimated for the center point of the area. These are monthly with categories of below 32-degrees, below 65 degrees, and above 65-degrees.

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This Web site is maintained by R. H. Giles, Jr.
Last revision July 20, 2001.