Tahun tropis (juga tahun matahari) merupakan tahun yang didasarkan pada revolusi bumi terhadap titik musim semi, yaitu terhadap awal berbagai musim. Tahun ini lamanya rata-rata 365.2421 siang hari atau 365 hari 5 jam 48 menit 46 detik.

Referensi

• Astronomical Applications Dept. of United States Naval Observatory. (2009). Multiyear Interactive Computer Almanac (ver. 2.2). Richmond VA: Willman-Bell.
• Blackburn, B. & Holford-Strevens, L. (2003, corrected reprint of 1999). The Oxford companion to the year. Oxford University Press.
• Borkowski, K. M. The tropical year and the solar calendar. (1991). Journal of the Royal Astronomical Society of Canada, 85(3), 121–130.
• Bureau International des Poids et Mesures. (2006). The International System of Units. Diarsipkan 2009-10-01 di Wayback Machine. author.
• Butrica, A. J. (1996) NASA SP-4218: To See the Unseen - A History of Planetary Radar Astronomy. NASA.
• Dershowitz, N. & Reingold, E.M. (2008). Calendrical Calculations (3rd ed.). Cambridge University Press. ISBN 978-0-521-70238-6
• International Earth Rotation Service (2010, January 28). Bulletin A 23(4) Diarsipkan 2015-03-14 di Wayback Machine.. author.
• Jet Propulsion Laboratory. (2005). DSN: History Diarsipkan 2010-08-07 di Wayback Machine.. author.
• Laskar, J. (1986). Secular terms of the classical planetary theories using the results of general theory. Astronomy and Astrophysics, 157, 59–70. ISSN 0004-6361.
• McCarthy, D. D. & Seidelmann, P. K. (2009). Time from Earth rotation to atomic physics. Weinhein: Wiley-VCH Verlag GmbH & Co. KGaA.
• Meeus, J. & Savoie, D. (1992). The history of the tropical year. Journal of the British Astronomical Association, 102(1), 40–42.
• Morrison, L. V. & Stephenson, F. R. (2004). Historical values of the Earth's clock error ΔT and the calculation of eclipses. Journal for the History of Astronomy Vol. 35, Part 3, No. 120, p. 327–336
• Newcomb, S. (1898). Tables of the four inner planets (Vol. 6) in Astronomical papers prepared for the use of the American ephemeris and nautical almanac (2nd ed.). Washington: Bureau of Equipment, Navy Dept.
• North, J. D. (1983). The Western calendar - "Intolerabilis, horribilis, et derisibilis"; four centuries of discontent. In G. V. Coyne, M. A. Hoskin, & O. Pedersen (Eds.). Gregorian reform of the calendar. Vatican Observatory.
• Seidelmann, P. K. (Ed.). (1992). Explanatory supplement to the Astronomical almanac. Sausalito, CA: University Science Books. ISBN 0-935702-68-7
• tropic. (1992). American Heritage Dictionary, 3rd ed. Boston: Houghton-Mifflin.