In the DICTIONARY OF TECHNICAL TERMS FOR AEROSPACE USE Web edition, edited by Daniel R. Glover, NASA Lewis Research Center Cleveland/Ohio, we can read under the term tropical year :

"The period of one revolution of the earth around the sun, with respect to the vernal equinox. Because of precession of the equinoxes, the tropical year is not 360 degrees with respect to the stars, but 50 minutes 0.3 seconds less. A tropical year is about 20 minutes shorter than a sidereal year, averaging 365 days 5 hours 48 minutes 45.68 seconds in 1955 and is increasing at the rate of 0.005305 second annually. Also called astronomical, equinoctial, natural, or solar year."

http://roland.lerc.nasa.gov/~dglover/dictionary//content.html

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"In present-day astronomy, the tropical year is defined as the time interval needed for the mean tropical longitude of the Sun to increase by 360 degrees."

(Journal of the British Astronomical Association V102, #1, 1992)

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Formulae for the 360-degree orbital period:

t360° = tsid ÷ [1 - (tsid ÷ tsol)]

t360° = tsol ÷ [(tsol ÷ tsid) - 1]

Where:

t360° = mean time period for the absolute center of the Earth to make a 360° revolution around the absolute center of the sun

tsid = mean time period of Earth's absolute rotation on its axis; i.e mean sidereal day of 86164.0905382 s or 1296000 arc-seconds

tsol = mean time period of Earth's complete rotation relative to the sun; i.e. mean solar day of 86400 seconds

It follows:

t360°= 86164.0905382 s ÷ [1 - (86164.0905382 s ÷ 86400 s)] = 31 556 925.97 s

t360°= 86400 s ÷ [(86400 s ÷ 86164.0905382 s) - 1] = 31 556 925.97 seconds

q.e.d.

Professional Astronomers claim that the length of the sidereal year (i.e. the time period for the absolute center of the Earth to make a complete 360° revolution around the absolute center of the sun) depends upon the adopted value of the lunisolar precession and is about 1223 seconds longer than the defined time period of the tropical- or sidereal year for 1900.0.

...Extraordinary Claims Demand Extraordinary Proof !