ISO周日歷
與格里歷關系
如果格里歷年的第一天是星期五、星期六和星期日,或是星期六和星期日,或正好就是星期日是格里歷年的第一天(在ISO年是去年的最后一天);又或者是星期一、星期二和星期三,或者是星期一和星期二,或正好就是星期一在格里歷年的最后一天(是下一個ISO年的第一個星期),ISO周數年的年份會偏離格里歷的年份。從1月4日至12月28日,ISO周數年和所有星期4的周數都會與格里歷相同。
第一周
ISO 8601定義包含當年第一個星期四的那一周是第一個星期。 基于這個定義,下列的屬性有相互的等價性:
第一周至少有4天在1月里面。
最接近格里歷年開始的是1月1日是星期一。.
第一個星期最早是12月29日至1月4日,最晚是1月4日至1月10日。
如果1月1日和星期六與星期日不是工作日,1月4日就會是第一個工作日。
如果1月1日是星期一、二、三、或四,它就是第一周,如果1月1日是星期五,它就是去年度的第53周;如果是星期六,它是去年第52周的一部分(如果上一年是格里歷的閏年,它就是第53周的一部分);如果是星期日,它是去年第52周的部分。
最后一周
ISO周日歷的最后一星期是第52周或53周,是下一年的第一周之前。這一周的特質如下:
格里歷的最后一個星期四會在這一周內。
最后一周有至少有4天在12月里面。
它的中間日,星期四,一定在年尾。
最接近格里歷年結束的是12月31日星期日。
12月28日一定在年度內。因為最后一周的日期最晚是12月28日至1月3日,最早是12月21日至12月28日。
如果12月31日是星期一、二、或三,它是下年度的第一周;如果是星期四,它會是結束結束的第53周;如果是星期五,它是年度的第52周(或是在閏年的第53周);如果是星期六或星期日,它是結束年度的第52周。
每年的星期
長年 ,是有53星期的年,可以有下列與定義等效的敘述:
任何從星期四開始的年(主日字母D或DC)和以星期三開始的閏年(ED)。
任何以星期四結束的年(D、ED)和以星期五結束的閏年(DC)
在1月1日和12月31日(在平年)或其中之一(在閏年)是星期四的年度。
其它所有的ISO周日歷的年都是只52周的 短年 。
再給定的年度中,12月28日對應的周數就是當年的星期數目。
平均而言,每5.6388……年(=7/[365.2425 – 52 X 7] = 400/71有一年是53周的長年。一年的長度是On average, a year has 53 weeks every 5.6338… years (= 7 / [365.2425 ? 52×7] = 400 / 71).
下面的71年是400年循環(huán)(加上2,000就是本世紀的年度)中有53周的年度(需要注意閏年有2月29日),未列出的年份僅有52周:
ISO的常年有43次間隔6年,27次間隔5年,有一次間隔7年(從296年到303年)。
格里歷年與這71個長年的對應關系可以細分如下:
27個格里歷的閏年(366天,在儒略歷也是閏年)。 Gregorian leap years (366
44個平年(365天,相較于儒略歷也是平年)開始和結束都是星期四。
格里歷對應于短年的ISO周日歷(無論開始或結束都不是星期四)的其余329年,可以細分敘述如下:
有70個閏年(對應的儒略歷年也都是閏年),和
259個平年(但是儒略歷有3年是閏年:100、200、和300)。
因此,在400年的循環(huán)中:
27個ISO周日歷的長年(53周或371天)比對應的格里歷閏年(366天)多5天。
44個ISO周日歷的長年(53周或371天)比對應的格里歷平年(365天)多6天。
70個ISO周日歷的短年(52周或364天)比對應的格里歷閏年(366天)少2天。
259個ISO周日歷的短年(52周或364天)比對應的格里歷平年(365天)少1天。
每個月的星期
ISO的標準并未定義任何周與月相關聯的協定。月中的每一天和月,也都以周和周日表達,且不會混淆不清。
在會計年度中,周年統(tǒng)計受益于星期是一個顯著實體的規(guī)則。因此,在實務中通常每一季固定有13個星期,并且分割成5+4+4周、4+5+4周、或4+4+5周。在53個星期的長年中,最后一季有14個星期。
雖然ISO 8601認為沒有這樣的需要,但在有必要將星期分配到一個月中的時候,可以應用的規(guī)則是從每年的第一個星期開始。由這種模式產生的結果,會是不規(guī)則的。有4個月(或在長年有5個月)會有5個星期,但是至少有29天是從星期四開始,30天是從星期三開始,31天從星期二開始。
Dates with fixed week number
For all years, 8 days have a fixed ISO week number (between 01 and 08) in January and February. And with the exception of leap years starting on Thursday, dates with fixed week numbers occurs on all months of the year (for 1 day of each ISO week 01 to 52) :
During leap years starting on Thursday (i.e. the 13 years number 004, 032, 060, 088, 128, 156, 184, 224, 252, 280, 320, 348, 376 in a 400-year cycle), the ISO week numbers are incremented by 1 from March to the rest of the year (this last occurred in 1976 and 2004 and will not occur before 2032; these exceptions are happening between years that are most often 28 years apart, or 40 years apart for 3 pairs of successive years: from year 088 to 128, from year 184 to 224, and from year 280 to 320).
The day of the week for these days are related to Doomsday because for any year, the Doomsday is the day of the week that the last day of February falls on. These dates are one day after the Doomsdays, except that in January and February of leap years the dates themselves are Doomsdays. In leap years the week number is the rank number of its Doomsday.
Equal weeks
The pairs 02/41, 03/42, 04/43, 05/44, 15/28, 16/29, 37/50, 38/51 and triplets 06/10/45, 07/11/46, 08/12/47 have the same days of the month in common years. Of these, the pairs 10/45, 11/46, 12/47, 15/28, 16/29, 37/50 and 38/51 share their days also in leap years. Leap years also have triplets 03/15/28, 04/16/29 and pairs 06/32, 07/33, 08/34.
The weeks 09, 19–26, 31 and 35 never share their days of the month with any other week of the same year.
優(yōu)點
All weeks have an integral number of days (i.e. there are no fractional weeks).
All years have an integral number of weeks.
The date directly tells the weekday.
All week-numbering years start with a Monday and end with a Sunday.
When used by itself without using the concept of month, all week-numbering years are the same except that some years have a week 53 at the end.
The weeks are the same as used with the Gregorian calendar.
計算
計算給定日期的周數
The week number of any date can be calculated, given its ordinal date (i.e. position within the year) and its day of the week. If the ordinal date is not known, it can be computed by any of several methods; perhaps the most direct is a table such as the following.
Method: Using ISO weekday numbers (running from 1 for Monday to 7 for Sunday), subtract the weekday from the ordinal date, then add 10. Divide the result by 7. Ignore the remainder; the quotient equals the week number. If the week number thus obtained equals 0, it means that the given date belongs to the preceding (week-based) year. If a week number of 53 is obtained, one must check that the date is not actually in week 1 of the following year.
Example: Friday 26 September 2008
Ordinal day: 244 + 26 = 270
Weekday: Friday = 5
270 ? 5 + 10 = 275
275 / 7 = 39.28…
Result: Week 39
計算給定日期的年、周數和周日
This method requires that one know the weekday of 4 January of the year in question. Add 3 to the number of this weekday, giving a correction to be used for dates within this year.
Method: Multiply the week number by 7, then add the weekday. From this sum subtract the correction for the year. The result is the ordinal date, which can be converted into a calendar date using the table in the preceding section. If the ordinal date thus obtained is zero or negative, the date belongs to the previous calendar year; if greater than the number of days in the year, to the following year.
Example: year 2008, week 39, Saturday (day 6)
Correction for 2008: 5 + 3 = 8
(39 × 7) + 6 = 279
279 ? 8 = 271
Ordinal day 271 of a leap year is day 271 ? 244 = 27 September
Result: 27 September 2008
其他的周數系統(tǒng)
For an overview of week numbering systems see week number.
The US system has weeks from Sunday through Saturday, and partial weeks at the beginning and the end of the year, i.e. always 53 weeks. An advantage is that no separate year numbering like the ISO year is needed. Correspondence of lexicographical order and chronological order is preserved (just like with the ISO year-week-weekday numbering), but partial weeks make some computations of weekly statistics or payments inaccurate at end of December or beginning of January.
A variant of this US scheme groups the possible 1 to 6 days of December remaining in the last week of the Gregorian year within week 1 in January of the next Gregorian year, to make it a full week, bringing a system with accounting years having also 52 or 53 weeks and only the last 6 days of December may be counted as part of another year than the Gregorian year.
The US broadcast calendar counts the week containing 1 January as the first of the year, but otherwise works like ISO week numbering without partial weeks.
相關條目
星期
4-4-5歷
Template:Chronology
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