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In the context of this article, when we say day, we are referring to the 24-hour interval in which the earth makes a complete rotation about its axis. This interval includes a day and a night if we separate them in the intervals in which it is light (day) and in which it is dark (night).
The Gregorian Calendar used today was introduced in 1582. However, its history dates back to Roman times.
In the Roman Calendar, ordinary years had 355 days. Systematically, years of 377 or 378 days should have been interspersed between them, to maintain alignment with the tropical year. However, often, dignitaries avoided doing so, or did so for 2 consecutive years (for political reasons, for example, to extend their political mandates).
To end these disturbances, in the year 46 BC, Julius Caesar proposed that from January 1, 45 BC, a new version of the Roman Calendar be applied. The Greek astronomer Sosigenes of Alexandria advised him on this and designed the calendar reform.
To facilitate the adoption of the new calendar, the year 46 BC was extended several times and lasted 445 days. This had to be done to align the beginning of the tropical year with January 1, 45 BC. Because ordinary citizens usually had no idea what the current date was, the year 46 BC has been called the "last year of confusion."
In time, however, the days of the year shifted due to certain astronomical events, as the Julian Calendar estimated the solar year to be 11 minutes and 14 seconds shorter than it actually is.
In 1582, Pope Gregory XIII hired the German Jesuit and astronomer Christopher Clavius to solve this problem. Following Clavius’s research and discoveries, the Gregorian Calendar was created and put into practice immediately.
The 10 days lost over time due to the gap between the solar year and the Julian Calendar were recovered when it was decreed that after October 4, 1582, the next day would be October 15.
From then on, we have used this calendar. The only adjustment is the one that was made in the 20th century, stating that if a year is divisible by 400, it would not be considered a Leap Year. This was decided because, according to the current Gregorian Calendar, one more day should be added once every 3,323 years.
To answer this question, we need to look into the field of astronomy.
The time interval in which the earth makes a complete rotation around the Sun is called the solar year and it is 365.242199 days long—in other words, 365 days 5 hours 48 minutes and 46 seconds.
Because this astronomical event does not happen in an exact unit of time, conventions have been established regarding the number of days in a calendar year.
The Gregorian Calendar introduced in 1582 was accepted and still functions as a worldwide convention. It states that for three consecutive years, only 365 days will be taken into account, while in the fourth year, the remaining difference will be added up (4 x 0.25 days). This fourth year will have 366 days.
For example, the years 2017, 2018, and 2019 had 365 days, while 2020 had 366 days. Respecting the same rule, 2021, 2022, and 2023 will each have 365 days, and 2024 will have 366 days.
All years that have 366 days are called Leap Years, and the "extra" day is February 29. Therefore, this day will exist only once every four years.
As we have seen, every four years, a day is added to our calendar to synchronize the solar year with the calendar year. According to this convention, the added day is February 29 and because it is added in a Leap Year, in turn, it is called a Leap Day.
In the three normal years, February has 28 days, while in the fourth year, it has 29 days.
Out of 7.7 billion people worldwide, about 5 million were born on February 29. Among them are the following celebrities:
People born on February 29 may celebrate their birthday on their real birth-day only once every four years,
they grow old just like the rest of us.
As 29 comes after 28, legally speaking, the age is considered to be fulfilled with the passing of February 28th. Therefore, on a "normal" year, this date will be March 1.
The number of days differs from month to month. The basic idea is that the lunar calendar reflects the time interval in which the Moon makes a complete orbit around the Earth, which is 29.53 days. The ancient Greek month started once the first segment of the new moon appeared. But the Moon's motion in its orbit is not constant, so it was very difficult to predict when one calendar month would end and the next would begin. Therefore, the number of days in a calendar month was not easy to determine.
Subsequently, the earliest ancient Roman calendars used months with 29 or 30 days, and as we have seen, the calendars were reformed more than once. In the end, the number of days that Julius Caesar set in 46 BC has remained unchanged to this day.
We still use this calendar template, which has 31 days for seven months, 30 days for four months, and 28 (or 29 in a Leap Year) days for February.
There are seven days a week. Why this number, and not more or less? Simply because this convention has been used since antiquity.
Unlike the day, month, or year, this seven-day time interval does not correspond to any astral event.
However, the seven days of the week still seem to be related to astrological events. The Babylonians celebrated "holy days" on certain days according to the new moon (the 7th, 14th, 21st, and 28th) and also the full moon (sabbath).
From ancient times, there have been differences in the days on which the week begins. To this day, in some
countries, the week begins on Sunday, while in others it begins on Saturday.
For example, in North America, Sunday is the first day of the week, while modern Western culture refers to Monday as the beginning of the workweek. In Europe, Monday is considered the first day of the week.
remove doubts that can result from the various day–date conventions, cultures, and time zones that impact a global operation.
Babylonians, just like the ancient Greek and Roman civilizations, recognized seven planets in the sky. These are the ones visible to the naked eye, namely, the Sun and the Moon, as well as Mars, Mercury, Jupiter, Venus, and Saturn. Therefore, they named the days of the week after these objects.
It is worth mentioning that the order of these planets, the way they move in the sky, and their distance from the earth has no relevance with regard to the order in which the days of the week were named.
Although in many cultures the days of the week are named after these planets, there are also cultures in which the days of the week are named after certain deities.
Alchemists have associated each of the seven planets after which the days of the week are named with different metals and vital organs over which they supposedly hold dominion.
The associations are the following:
Nowadays, we are familiar with similar associations in the field of astrology.
This pseudoscience claims
that it is possible to predict the course of affairs in our lives by studying the movements of astral
Astrology makes these associations between the supposed influences that the planets have on us as well as the characteristics of the deities that govern those planets. Thus, regarding the seven days of the week, astrological theories were issued according to which:
Regarding professional activity, it was established that out of the seven days of a week, five of them would be worked on, while the other two would be allocated to professional rest.
Although this convention is not universally valid, it is generally considered to be:
Depending on the circumstances, sometimes labor is done on Saturdays and Sundays, and the professional rest is taken on two other days of the week. However, in general, when we talk about weekdays, we mean the days listed above.
Saturdays and Sundays have been considered days of religious worship and rest since antiquity. However, this is not the same in all religions. For example, Saturday is a day of religious celebration (Sabbath) for Jews, Seventh-Day Adventists, Messianics, and Seventh-Day Baptists. Instead, for the Roman Catholic and Eastern Orthodox churches, Sunday is the Lord's day.
Apart from the religious holidays celebrated over the year by believers of different religions, certain dates
have been established as being legal holidays.
Usually, on these days a certain event is celebrated, or the days mark dates when something remarkable happened in the history of the country that decreed the dates to be holidays.
For example, in the US, the first legal holidays were instituted in 1870. These were New Year’s Day, Independence Day, Thanksgiving Day, and Christmas Day.
Later, others were added. There are currently 12 permanent federal holidays in the United States.
A school year, also called an academic year, is a period of time in a calendar year in which students must attend school. Except for public holidays and breaks or vacations, in the US the school year consists of 160 to 180 days. It should be noted that each state designates a minimum number of days and hours.
For example, most states established that there will be a minimum of 180 school days in 2021. But there are exceptions, including:
Several factors can influence the number of workdays in a year. These can be:
Taking all this into account, the following are the number of working days in 2021, 2022, and 2023:
The year we discussed in this article is the calendar year.
But there are other expressions in which the word "year" is used to define a certain time interval, such as:
In astronomy, there are also several types of years and each of them has a different meaning and duration.
Contributor at PlanArty