Claim: A South African paper has found a 21 year cycle synchronous with the solar cycle (Alexander 2007).

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: The Milankovitch cycles are a set of cyclic variations in characteristics of the Earth's orbit around the Sun.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: A leap year (also known as an intercalary year or bissextile year) is a calendar year containing an additional day (or, in the case of lunisolar calendars, a month) added to keep the calendar year synchronized with the astronomical or seasonal year.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: The Bahá'í calendar is a solar calendar composed of 19 months of 19 days each (361 days).

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Orbital forcing from cycles in the earth's orbit around the sun has, for the past 2,000 years, caused a long-term northern hemisphere cooling trend that continued through the Middle Ages and the Little Ice Age.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: One comprises what we have called "Saros Cycle Texts", which give the months of eclipse possibilities arranged in consistent cycles of 223 months (or 18 years).

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The solar cycle is a 28-year cycle of the Julian calendar with respect to the week.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Solar sunspot maximum occurs when the magnetic field of the sun collapses and reverse as part of its average 11 year solar cycle (22 years for complete North to North restoration).

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: There are some recent speculations that cycle 4, the longest solar cycle since 1755, was actually two cycles, based on the appearance of new sunspots at high solar latitudes in 1793-1796 and a reconstruction of the sunspot butterfly diagram for cycles 3 and 4, although total sunspot numbers only show a single-peaked distribution.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The oscillation in the Z direction takes the Sun ( W ( 0 ) ν ) 2 + Z ( 0 ) 2 = 98  parsec {\displaystyle {\sqrt {\left({\frac {W(0)}{\nu }}\right)^{2}+Z(0)^{2}}}=98{\text{ parsec}}} above the galactic plane and the same distance below it, with a period of 2 π / ν {\displaystyle 2\pi /\nu } or 83 million years, approximately 2.7 times per orbit.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: "Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature" (PDF).

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Third, the Earth is at aphelion in July (i.e., the Earth is farthest from the Sun in the Antarctic winter), and the Earth is at perihelion in January (i.e., the Earth is closest to the Sun in the Antarctic summer).

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: A tropical year (also known as a solar year) is the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Apsidal precession combines with the 25,771.5-year cycle of axial precession (see above) to vary the position in the year that the Earth reaches perihelion.