Expired calendars can be extended to 20 15. In what year?

"If you happen to dig out an old calendar of 1986, you can dust it because it is exactly the same as the calendar date of 20 14." 20 14 at the beginning of the new year, the news spread wildly on the internet made countless nostalgic people flock to it, and even more savvy businessmen found business opportunities and sold the old calendars that had been baptized by years. Some netizens said that calendars can be recycled once every 28 years. So is this statement reliable?

1986 calendar is still available this year.

The reporter rummaged through these two years in the calendar and found that 1986 and 20 14 both started on Wednesday and ended on Wednesday. From the beginning of the year to the end of the year, the date and week are relative without any deviation. Of course, the so-called sameness refers to the Gregorian calendar. According to the lunar calendar in China, the dates of these two years have a deviation of 10 day.

Surprisingly, the old calendar after nearly 30 years is exactly the same as the new calendar. But if we carefully compare the calendars of the past 30 years, the reporter found that this situation has happened several times. For example, the calendars of 1997 and 2003 are also the same as those of 20 14. In these years, the calendar date of 2003 is not only the same as that of 20 14, but also the difference between the lunar calendar and 20 14 is only about 2 days. If someone wants to replace the old calendar, there is no doubt that the calendar in 2003 is the most suitable.

Not only has this happened before, but the time has been pushed back 1 1 year. By 2025, the calendar will be common with this year, and by that year, the difference of the lunar calendar will be only 1 day.

"Tidy up the past calendar, wait until the date of a certain year is the same, and then take it out. Maybe it has a charm. "

Nostalgic calendars explore business opportunities on the Internet.

Looking at the calendar more than 20 years ago, I feel that the years have passed in my hands, and there is a different kind of beauty in my trance. For some people born in that year, such an old calendar has different meanings. Seeing such business opportunities, on some shopping websites, merchants quickly hang up carefully collected old calendars or provide "privately customized" exclusive calendars.

On a shopping website, the reporter typed in the words "calendar 1986" and quickly searched out more than 30 stores. Some of these shops hang old calendars collected from flea markets, and the covers are female stars who were very popular in that era. Even if it's just an online effect map, the precipitation of a year can still be expressed through the folds on the calendar. Generally, the hanging price of such calendars ranges from 100 to 200 yuan.

After all, there are not many calendars that can withstand the baptism of time. Even if it is preserved, it is damaged. Some merchants have put up the signboard of "personal tailor", which can manufacture and sell a batch of calendars according to customers' requirements and polish them by technical means. The content of the calendar can be the popular people and events of the year, or it can be completely according to the needs of customers. The price of each book is about 100 yuan.

Many people may not know the repetition of dates. Whether it is an old calendar or a custom calendar, there is almost no transaction recently.

Although I was fired because of business opportunities, it is really not easy to find the old calendar of that era. "Calendars after 1980 are rarely collected unless they have special significance." Mr. Ding, a collector in Hefei, told the reporter that at present, there are no enthusiasts who specialize in collecting calendars in Hefei, and there is no special trading market. If you want to collect old calendars, you can only go to the second-hand book market to exchange them. "Sometimes you can't see them."

Mr. Ding said that the calendars that can attract collectors' interest at present mainly have a certain year. For example, during the Republic of China and the "Cultural Revolution", he had several calendars of that period in his hand, and the longest time was nearly 100 years ago. "At that time called almanac. In addition to the date, there will be some knowledge at that time. " The value of these calendars is just above the knowledge of cultural customs at that time, because they have different preferences and are not easy to evaluate.

Calendars can be recycled every 28 years?

"You know, calendars are the same every 28 years? It is better to reuse the old calendar, which is very environmentally friendly! " Some netizens confirmed the authenticity of this statement through calculation.

Netizens say that there are 365 days in a year, and 365 divided by 7 equals 1 52 more (that is, there are 52 weeks 1 day in a year). So the same day in the second year is the week of the year plus 1. And if that year is a leap year, a year is 366 days, that is, 52 weeks and 2 days, then you need to add 2 days to the number of weeks in the previous year.

After four years, there will be three normal years and 1 leap year, so the number of weeks will be moved forward by five days every four years. Then, after 74 years, that is, after 28 years, the week number will move by 35 days. Since 35 is an integer multiple of 7, the number of weeks just moves back, completing a cycle.

So, is the netizen's algorithm correct? Relevant experts said that this algorithm has some truth, but it is not all right. "It ignores the problem that a year is not a complete 365 days."

Since the Gregorian calendar is based on the tropical year, a tropical year is about 365 and a quarter of a day, and the accuracy should be 365.438+099 days-of course, you can further improve the accuracy. In other words, there are actually 365.438+099× 4 ≈ 1460.97 days every four years. Therefore, according to the calculation of 365 days per year, there will be one less day every four years, and leap years will be born on demand.

However, adding leap days would be "overkill" and add 0.03 days to the calendar. This 0.03 days doesn't seem to matter much, but there will be 3 more days every 400 years, which needs to be revised again. So a special rule is added to the calendar: if the last two digits of the year are 00, it depends on whether the first two digits are divisible by 4. In this way, 1700, 1800 and 1900 are not leap years, but only years like 1600 and 2000 are leap years. This law can reduce three leap years from every 400 years, which is roughly in line with the actual situation.

It can be seen that the statement that the calendar based on "four-year leap" has a 28-year cycle is problematic, and it is only useful in 100. "From 2000 to 1999, the calendar of 100 followed the principle of a cycle of 28 years, but by 2 100, this statement had not been established and entered.

"If you don't consider the lunar calendar and reuse the Gregorian calendar, you don't need to wait for 28 years!" According to experts, it is only necessary to prepare 14 calendars to recycle calendars.

According to reports, the correspondence of calendars mainly refers to the correspondence between dates and weeks, that is, it is related to what day is the first day of a year and whether it is a leap year. In other words, there are only 14(7×2) calendars in essence. Find out that 65438+ 10 month 1 is Monday, Tuesday, Wednesday and Sunday, with seven calendars in a normal year and seven calendars in a leap year. As long as this 14 calendar is collected, it will correspond to the actual situation of that year and become a complete "eternal calendar".

However, the above practices all refer to the corresponding relationship between the Gregorian calendar and the week. If we combine the lunar algorithm, the situation will be complicated.