day (23 hours, 56 minutes, 4 seconds), whether visible at night or obscured in daylight. Unlike the stars, the Sun and Moon do not have a fixed declination. Since Earth's rotational axis is tilted by about 23.5° with respect to a line perpendicular to its orbital plane (the ecliptic), the Sun's declination ranges from +23.5° at the June solstice to −23.5° at the December solstice, as the Earth orbits the Sun once every tropical year. Therefore, in June, in the Northern Hemisphere, the midday Sun is higher in the sky, and daytime then is longer than in December. In the Southern Hemisphere, the situation is reversed. This obliquity causes Earth's seasons. The Moon's declination also changes, completing a cycle once every lunar nodal period of 27.212 days. Thus, lunar declination ranges from a positive value to a negative one in just under two weeks, and back. Consequently in under a month, the Moon's altitude at upper culmination (when it contacts the observer's meridian) can shift from higher in the sky to lower above the horizon, and back. Thus the Moon's declination varies cyclically with a period of about four weeks, but the amplitude of this oscillation varies over an 18.6 year cycle. A lunar standstill occurs at the points in this latter cycle when this amplitude reaches a minimum or a maximum. The Moon differs from most natural satellites around other planets in that it remains near the ecliptic (the plane of Earth's orbit around the Sun) instead of Earth's equatorial plane. The Moon's maximum and minimum declination vary because the plane of the Moon's orbit around Earth is inclined by about 5.14° with respect to the ecliptic plane, and the spatial direction of the Moon's orbital inclination gradually changes over an 18.6-year cycle, alternately adding to or subtracting from the 23.5° tilt of Earth's axis. Therefore, the maximum declination of the Moon varies roughly from (23.5° − 5° =) 18.5° to (23.5° + 5° =) 28.5°. At the minor lunar standstill, the Moon will change its declination during the nodal period from +18.5° to −18.5°, for a total range of 37°. Then 9.3 years later, during the major lunar standstill, the Moon will change its declination during the nodal period from +28.5° to −28.5°, which totals 57° in range. This range is enough to bring the Moon's altitude at culmination from high in the sky to low above the