Equation of time ET--Algorithm 1.12The Equation of Time describes
variation between clock time and solar time due to eccentricity in the earth�s
orbit. ET is positive when sun time is before clock time. Like solar
declination, ET depends on the leap year cycle, but the following equation is
accurate to within 40 seconds.
- Day number, J
- J=1 on 1 January, J=365 on 31 December. February is taken to
have 28 days.
- The argument of the sine function is in radians.
- IES (1)
- IES Calculation Procedures Committee Recommended practice for the
calculation of daylight availability Journal of the Illuminating Engineering
Society of North America 13 (4) 381-392 (1984)
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