As a result, if you utilized an exact lunar calendar, you would lose 11 days every year in comparison to the widely used Gregorian Calendar. This is due to the Earth's 365-day orbit around the sun. Using this metric, lunar calendars are 10 times more accurate than the Gregorian Calendar.
A lunar calendar is usually based on the moon's 29.53-day synodic orbit around Earth. The year is then split into 12 lunar months, for a total of 354 days every year, or about 11 days fewer than the time it takes the Earth to complete one full cycle around the sun: 365 days. The extra day at the end of February each year is called a "leap day".
Lunar years are calculated by adding up the number of lunations (full moons) since January 1st. They can only be positive numbers, and they always include a repeat month (April or March). For example, since January 1st 2012 has had three full moons, its lunar year is 30 times 12 plus 2, or 360 + 2 = 362 days.
The lunar year is not exactly equal to the solar year, but rather closer to half of it. The difference grows larger as we go further into the past or future, due to an effect known as "lunation drift". Every 100 years or so, the moon is found to be drifting farther from the Earth - traveling 10 miles farther away during the current lunar cycle. This results in each new moon being slightly smaller than last night's, which adds up over time for all the previous full moons that were measured. Since 1912, when this was first noted, the amount of drift has been increasing slowly but steadily.
A solar year (the time it takes Earth to orbit the sun) lasts approximately 365 days, but a lunar year (the time it takes the moon to complete 12 full cycles) lasts around 354 days. Because of this difference, a solely lunar calendar, such as the Islamic, or Hijri, calendar, does not remain in sync with the seasons. Rather, the Islamic calendar changes each year to match the seasons; for example, when the spring equinox arrives at a different time each year, the Muslims adjust their prayers and fasting requirements accordingly.
Lunar months were originally based on the phases of the moon, but over time they were also used to denote periods of time equal to fractions of the lunar year. For example, the word "quincentenary" comes from the Latin meaning "fifth century". The period specified by this term would be approximately 35 Lunar Months after the first new moon of the year.
Solar weeks were originally based on the movements of the sun, but eventually became associated with the phases of the moon. A solar week is calculated as the interval between two successive full moons. Because of this relationship, a lunar month cannot contain the same number of days as a solar month because there will always be more than one full moon in a solar month, but there can be only one full moon in a lunar month.
The lunar calendar has the benefit of being substantially more accurate than the solar calendar in terms of seasonal occurrences. The Lunar calendar did not change throughout time. It is the most basic and natural form of a date calendar. To recap, the Lunar calendar predates the Moon itself. It is calculated based on how many days are contained in the full moon or new moon.
In addition, because it is based on the cycle of the moon, there is no need for humans to adjust the calendar at all. The lunar calendar is perfect because it is always in phase with the seasons. This means that each month will contain exactly 30 days of sunlight and darkness. There are several reasons why the solar calendar is not like this by nature: first, because it is based on the cyclical changes in the earth's orbit around the sun. These changes can be large enough to cause months to come up short or go past their due date if they are not corrected by adding or removing dates from the calendar. For example, if the spring equinox was on March 20th in 10BC it would not be until 1133AD that it would happen again! Second, because it is necessary to add dates to the solar calendar every year because of Earth's rotation around its axis. If we didn't do this, summer would arrive too early and winter too late every year!
Finally, the lunar calendar does not move away from the autumnal equinox.
The Gregorian calendar is based on the movement of the sun; one year is equal to one circuit around the sun. The lunar calendar is often 20–50 days later than the Gregorian calendar. The Chinese Lunar Date 'Feb 2' appears to be on both Gregorian dates, March 14 and 15. However, it isn't exactly same as Febuary 14 or 15 because the Chinese lunar calendar has its own time zone called "Lunar New Year's Day". This day varies from year to year because it is determined by the moon's position in relation to Earth.
In addition, the Chinese lunar calendar begins with a new moon and ends with a full moon. It is therefore a repeating cycle that lasts 29 or 30 days each time. The only exception is when the moon is either full or new, then it will stay in the same phase for several years in a row. A lunar eclipse will not occur until 2017 or 2020 depending on where you live. Out of town readers should know that if you are not used to seeing stars during a total lunar eclipse, you can see them through your local sky observatory!
Lunar eclipses were once considered omens and were used in traditional Chinese medicine. They are still regarded as significant in China and Japan. In fact, the Japanese word for moon, "yoko", comes from the word for eclipse, "yokugana".