Key Differences Between Solar and Lunar Calendars
A solar calendar can be best understood by visiting Jantar Mantar (Delhi, Jaipur).
There was a time when the inclination of sun rays helped people determine the time. Moreover, it also helped people determine the occurrence of an eclipse or any other happenings.
Usually, a solar calendar helps determine the occurrence on the basis of the time the earth takes to revolve around the sun.
In short, we can say that the solar calendar is a method of measuring and recording the time periods on the basis of the time earth takes to revolve around the star (Sun).
On this page, you will understand solar month, lunar calendar, and solar calendar.
What is a Solar Calendar?
A solar calendar is a calendar, the dates of which point to the season. They are almost equal to the apparent position of the Sun relative to the stars.
The Gregorian calendar is widely accepted as a standard calendar in the world.
The Gregorian calendar is a well-known example of a solar calendar.
Another important type of calendar is the lunar calendar.
In a lunar calendar, months correspond to cycles of Moon phases.
However, the months of the Gregorian calendar never correspond to cycles of the Moon phase.
There are various types of calendars that help determine the solar month; these are as follows:
Examples of Solar Calendars
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1. Tropical Solar Calendars
If the position of the world in its orbit around the Sun is estimated with reference to the Equinox, the purpose at which the orbit crosses the equinoctial circle, then it's dates accurately indicate the seasons.
It means they're synchronized with the declination of the Sun. Such a calendar is named a tropical solar calendar.
2. Sidereal Solar Calendars
When the position of the Earth is estimated with respect to the fixed stars, the dates indicate the zodiacal constellation near which the Sun can be found.
This type of calendar is the sidereal solar calendar.
3. Lunisolar Calendar
Lunisolar calendars are lunar calendars. As a rule, lunisolar calendars are the additional intercalation that keeps a rough synchronization with the solar year; also, with the seasons.
Ordinarily, a lunisolar calendar has a whole number of lunar months. However, it can't indicate the position of Earth on its revolution around the Sun. The same is with a solar calendar.
Lunar to Gregorian Calendar
Firstly, Egyptians developed the solar calendar to use the annual appearance of the Dog Star - Sirius.
Sirius coincided with the yearly flooding of the Nile River, as a focal point.
However, the Egyptians didn’t consider the extra part of a day in their 365-day calendar.
Later, Julius Caesar in favor of the Julian Calendar replaced the Roman republic calendar, based on the Lunar Calendar of the ancient Greeks.
Further, the Julian Calendar allowed for February as leap year; also, made the solar year too long by adding a quarter of a day annually.
By then, in the 16th Century, the additional time accumulated to form an error of around 10 days which was improvised in the form of the current Gregorian Calendar.
Solar Years Month
With the help of the solar calendar, we can predict the time period in which the sun sets and rises throughout the day. Besides this, throughout the year, we can also determine the occurrences of the lunar and solar eclipse.
Though the measuring of time started in India; so how the time determination occurred, let’s understand it:
Maharaja Jai Singh II of Jaipur established five Jantar Mantar in the early 18th century, the cities are:
New Delhi
Jaipur
Ujjain
Mathura
Varanasi;
These five were completed between 1724 and 1735.
The Jantar Mantar monuments have Samrat Yantra, Jai Prakash, Ram Yantra, and Niyati Chakra. Each of these is employed for various astronomical calculations.
The fundamental objective of the observatory was to compile astronomical tables. Also, to predict the days and movements of the sun, moon, and planets.
The List of Instruments Involved are:
Samrat Yantra
Jai Prakash Yantra
Disha Yantra
Rama Yantra
Chakra Yantra
Rashi Valaya Yantra
Dingash Yantra
Utaansh Yantra
Solar Years Month
Earth's revolution around the Sun defines the year in the Western World .Therefore, the earth's revolution is referred to as a ´Solar Year´. However, several varieties of Solar years exist:
Tropical Year
A Tropical Year is derived from the Greek word ‘tropia’, meaning the turning points.’ This year lasts 365.242199 days UT.
The name topical years refer to the changes of seasons that remain fixed in this kind of year.
Sidereal Year
A Sidereal Year lasts 365.256366 days UT. This year is the interval between two successive passages of the Mean Sun at the same star.
Lunar Calendar and Solar Calendar
A solar-lunar calendar carries a difference. Additionally, there is a feature that a lunar calendar upholds.
So, let’s get started with the difference between the lunar calendar and solar calendar:
Lunar Calendar
Talking about a lunar calendar, we usually have 354 days; however, in a leap year, a lunar calendar has 384 days.
Solar Calendar
A solar calendar has 365 days. In addition to it, there are 365 days, i.e., an additional day during a leap year.
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Additionally, a lunar calendar shifts quickly in contrast to a lunar calendar.
Give a List of Solar Calendars that are Used Currently or were Used in the Past
There are a number of examples of solar calendars available across the world. Some of these examples are the Assamese calendar, Astronomical year numbering, Assyrian calendar, Badi’ calendar, Bengali calendar, Basotho calendar, Berber calendar, Byzantine calendar, Bulgar calendar, Coptic calendar, Era Fascista, Discordian calendar, Ethiopian calendar, French Republic calendar, Florentine calendar, Gregorian calendar, Hanke-Henry Permanent Calendar, Holocene calendar, Indian national calendar, International Fixed Calendar, Invariable Calendar, Jalali calendar, Javanese calendar, Juche era calendar, Julian calendar, Malayalam calendar, Minguo calendar, Nanakshahi calendar, Odia calendar, Old Icelandic calendar, Pan Chronometer, Pataphysical calendar, Pax Calendar, Pentecontad calendar, Pisan calendar, Positivist calendar, Revised Julian calendar, Roman calendar, Runic calendar, Solar Hijri calendar, Soviet calendar, Swedish calendar, Symmetry454, Tamil calendar, Thai solar calendar, Tulu calendar, World Calendar, and World Season Calendar.
Do You Know?
An Islamic Calendar relies on the Lunar Calendar for ascertaining the dates of their festivals such as Ramadan and the pilgrimage to Mecca.
Therefore, the lunar to Gregorian calendar advances through our Gregorian solar calendar by 11 days every year.
FAQs on Solar Calendar in Physics: Meaning, Types & Examples
1. What is a solar calendar and how does it work?
A solar calendar is a timekeeping system based on the Earth's revolution around the Sun. It is designed to align with the seasons. The calendar year approximates the tropical year, which is the time it takes for the Earth to complete one full orbit, roughly 365.2425 days. To keep the calendar in sync with the seasons over time, an extra day (a leap day) is periodically added.
2. What are the main differences between a solar calendar and a lunar calendar?
The primary differences between solar and lunar calendars lie in their astronomical basis, length, and purpose:
- Basis: A solar calendar is based on the Earth's orbit around the Sun, while a lunar calendar is based on the phases of the Moon.
- Year Length: A solar year is approximately 365 days long. A lunar year, consisting of 12 lunar months, is about 354 days long.
- Seasonal Alignment: Solar calendars remain synchronised with the seasons. Lunar calendars, being 11 days shorter, drift out of sync with the seasons each year.
- Primary Example: The Gregorian calendar is the most common solar calendar, while the Islamic Hijri calendar is a prominent lunar calendar.
3. Why do solar calendars need a leap year?
Solar calendars require a leap year to correct a mathematical discrepancy. The Earth takes approximately 365.2425 days to orbit the Sun, but a standard calendar year has only 365 days. This leaves a remainder of about 0.2425 days each year. To prevent the calendar from drifting out of sync with the seasons, an extra day—the leap day on February 29th—is added every four years. This intercalation realigns the calendar with the Earth's position in its orbit.
4. What are some common examples of solar calendars used today?
The most widely used solar calendar is the Gregorian calendar, which is the international standard for civil use. Other significant examples of solar calendars include:
- The Iranian (Persian) calendar, which is considered one of the most astronomically accurate.
- The Indian National Calendar (Saka calendar), used for official civil purposes in India.
- The Julian calendar, the predecessor to the Gregorian calendar, still used by some Eastern Orthodox Churches.
- The Coptic calendar, used by the Coptic Orthodox Church of Alexandria.
5. Is the Gregorian calendar a type of solar calendar?
Yes, the Gregorian calendar is a prime example of a tropical solar calendar. It was specifically designed as a reform of the Julian calendar to better approximate the tropical year and keep the date of the spring equinox consistently around March 21st. Its system of leap years is precisely what defines it as a solar calendar, as its main purpose is to track the seasons accurately.
6. How is a 'solar calendar' different from the astronomical 'solar cycle'?
These two terms refer to completely different concepts and should not be confused. A solar calendar is a man-made timekeeping system used to track days, months, and years based on the Earth's orbit. In contrast, the solar cycle is a natural phenomenon referring to the approximately 11-year cycle of the Sun's magnetic activity, which is observed through changes in sunspots, solar flares, and coronal ejections.
7. What is the difference between a tropical solar calendar and a sidereal solar calendar?
The key difference is the reference point used to measure the year. A tropical solar calendar, like the Gregorian calendar, measures the year based on the time between two successive vernal (spring) equinoxes. Its primary goal is to stay aligned with the seasons. A sidereal solar calendar, like traditional Hindu calendars, measures the year based on the Sun's apparent position relative to the background of fixed stars. A sidereal year is about 20 minutes longer than a tropical year.
8. How does India's national calendar relate to the solar calendar system?
India's official civil calendar, known as the Saka calendar, is a tropical solar calendar. It was formally adopted in 1957 to be used alongside the Gregorian calendar. The days of the Saka calendar correspond one-to-one with the Gregorian calendar, with a leap day added in Chaitra, its first month, every four years. This ensures it remains synchronised with the tropical year and the seasons, just like other solar calendars.
