By glancing at the moon, you may determine the time of year or month. It alters its form or the quantity of light it emits. For example, you may tell a day has gone when the sun rises, the sky lightens, and the sun sets again. The full moon shows that it is night, and since the moon is visible in the daytime, you can tell the month is either right after the full moon or right before it (the exact timing depends on the phase of the moon). New moons appear dark because no sunlight is reflecting off of the surface while thin clouds often cover a lunar face when it is over halfway to full brightness.
Lunar cycles are important for determining history's flow of time. For example, the average length of a lunar month is about 29 days but this can range from 27 to 31 days. This means that every 12 months the amount of time that has passed will have changed differently. On top of this, the phases of the moon change too; when half of it is illuminated by the sun, it becomes bright enough to see from Earth. So not only does the appearance of the moon change over time but so does its ability to signal the start of a new period as well.
The moon also signals other events such as birthdays, holidays, and even an impending storm. Scientists have found evidence that ancient people noticed changes in the moon's shape or position and used this information to predict future events.
A lunar calendar is simply a calendar that is based on the lunar cycles. Because the average time between two new moons is 29.5 days, its months were designed to be either hollow (29 days) or full (30 days). Julius Caesar established this during the Roman Calendar revision. He divided the year into four equal parts, called seasons, and assigned each season to one of his three annual holidays. The other half of the year was left unprescribed, so it could be used as required.
In the Chinese calendar, the term "month" refers to a division of the year, not a unit of measurement. It is made up of a number of consecutive lunar months, which vary in length from 29 to 30 days. The exact duration of a lunar month is determined by the moon's monthly cycle: the closer the moon is to full moon, the longer the night will be and thus the more days there will be in the month. But because the moon's orbit is elliptical, not exactly circular, the actual number of daylight hours can vary from 12 to 14 depending on where the moon is in its orbit.
Lunar months were first used by the Babylonians, but they called them periods of restraint (or abstention). They began when the moon is new and ended when it is again full. These names were also applied to the months themselves for clarity.
The moon is the source of the notion of a month. To divide a year into increments, several cultures utilized months with durations of 29 or 30 days (or some other variation). The fundamental issue with this type of system is that moon cycles, at 29.5 days, do not split evenly into a year's 365.25 days.
The Gregorian calendar features four months of 30 days and seven months of 31 days. February is the only month that lasts 28 days in regular years and 29 days in leap years. From ten to twelve months
The length of the day and night is determined by the Sun's location in reference to the Earth. The fall equinox occurs on September 22. The summer solstice, or the longest day of the year, occurs on June 21. And the winter solstice, or the shortest day of the year, occurs on December 20.
Slightly over nine hours long, September 23rd is a day with less darkness than midnight and more daylight than 11:30 AM. The length of the day is about 1 million miles (1.5 million km), or 0.5% longer at its longest point and 0.4% shorter at its shortest point than it is at midday, when the sun is directly overhead.
In science fiction literature, days often are shown as having 12 equal hours, which is also true for March and 27th months. However, in general science fiction history, days are not necessarily shown as having 12 hours; instead, they can be assumed to have an arbitrary length while keeping track of time accurately.
September 23rd is included on some lists of longest days and shortest nights-length weeks. The day is 1.5% longer than itself at its longest point and 1.0% shorter at its shortest point than it is at midday.
The solar dates are associated with solar years and solar months, which are described as follows: the solar year contains 12 solar months, each with 31 solar dates. At the conclusion of each lunar month of just 29 days, a solar date is skipped. Furthermore, at the conclusion of each lunar year, a solar date is skipped. This occurs because the moon is not visible on all solar dates.
The solar year was originally based on the time it took for the sun to travel around the earth. Because the speed of light is known, when you know the distance between two points on Earth you can calculate how long it takes for information to be transmitted from one point to the other. In 1874, American astronomer William Henry Smyth showed that this distance is equal to 365.2422 days. Therefore, a solar year is exactly equal to 365.2422 days.
In practice, however, due to the eccentric orbit of Earth, this distance varies slightly from year to year. If we look at a sequence of solar eclipses that occur near the middle of our planet's year, we can estimate how much the distance has changed over time. On June 15, 2019 there will be a total eclipse of the sun visible from North America. It will be the longest total eclipse seen in the region since 1776.
Eclipses happen when the Moon blocks out part of the sun, usually when the Moon is close to the Earth.
Every year, there are two equinoxes, in March and September, when the sun shines directly on the equator and the lengths of day and night are about equal. At other times of the year, the length of day is greater than that of night.
Equinox occurs when the earth crosses the line between the orbits of Mars and Jupiter. Because the axis of the planet Earth is at a slight angle to its orbit around the Sun, each year it passes through a different point on this orbit: one near the center, called the Spring Equinox, and another near the edge, called the Fall Equinox. At these points, the days and nights are of equal length.
During a total solar eclipse, the moon blocks out the sun entirely, causing night to fall over a large part of the world for several hours. During a total lunar eclipse, the moon takes on a reddish color as it passes across the face of the Earth unilluminated by sunlight. This type of eclipse happens only during a full moon and can only be seen from within certain regions including parts of North America, South America, Africa, and Asia.
Equinoxes can be divided into two categories based on where they occur relative to the spring and autumn solstices.