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Weeks in a year

Weeks in a year

Weeks in a year

An ISO week-numbering year (also called ISO year informally) has 52 or 53 full weeks. That is 364 or 371 days instead of the usual 365 or 366 days. These 53 week years occur on all years that have Thursday as the 1st of January and on leap years that start on Wednesday the 1st. The extra week is sometimes referred to as a Leap week calendar leap week, although ISO 8601 does not use this term. During leap years starting on Thursday (i.e. the 13 years numbered 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 again 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.

WEEK

The US system has weeks from Sunday through Saturday, and partial weeks at the beginning and the end of the year, i.e. 52 full and 1 partial week of 1 or 2 days if the year starts on Sunday or ends on Saturday, 52 full and 2 single-day weeks if a leap year starts on Saturday and ends on Sunday, otherwise 51 full and 2 partial 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 the end of December or the beginning of January or both.

The exception to the "52 weeks" rule pops up if you're using a fancy academic journal or office wall planner; sometimes they number the weeks based on them running from Sunday to Saturday, or Monday to Sunday, breaking up the first and last weeks of the year to fit this mould. Although there are still only 52 weeks in the year, and time doesn't magically slow down**, the way a calendar like that counts fragments at the start and end of the year might mean that the weeks are numbered as high as 54.This is all based upon the Gregorian calendar (introduced back in 1582), which cycles every 400 years. If you want to go a step further and work out the average number of weeks in a year across the full Gregorian calendar, you'll find that a year works out at 365.2425 days. When divided by 7 it gives you a total of 52.1775 weeks.The week number (WW or woy for week of year) of any date can be calculated, given its ordinal date (i.e. day of the year, doy or DDD, 1–365 or 366) and its day of the week (D or dow, 1–7). (Source: en.wikipedia.org)

DAY

The US system has weeks from Sunday through Saturday, and partial weeks at the beginning and the end of the year, i.e. 52 full and 1 partial week of 1 or 2 days if the year starts on Sunday or ends on Saturday, 52 full and 2 single-day weeks if a leap year starts on Saturday and ends on Sunday, otherwise 51 full and 2 partial 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 the end of December or the beginning of January or both.The ISO week calendar relies on the Gregorian calendar, which it augments, to define the new year day (Monday of week 01). As a result, extra weeks are spread across the 400-year cycle in a complex, seemingly random pattern. (However, a relatively simple algorithm to determine whether a year has 53 weeks from its ordinal number alone is shown under "Weeks per year" above.) Most calendar reform proposals using leap week designs strive to simplify and harmonize this pattern, some by choosing a different leap cycle (e.g. 293 years).

Leap years exist to correct a small margin of error in our annual calendars. A complete orbit of the sun actually takes Earth 365 days and 5 hours, 48 minutes. To compensate for the extra time, every 4 years we add an extra day to the calendar to maintain accuracy (otherwise we would be out by 24 more days every century). In 1752, Europe was using the more accurate Gregorian calendar, which we still use today, but Britain was dragging its heels with the Julian calendar. The big switch happened in September that year, but to catch up with everyone else and to correct the accrued inaccuracy of the Julian calendar, English folk went to bed on Wednesday 2nd September 1752, and woke up on Thursday 14th September 1752. Some sources claim that members of the public rioted, outraged that their lives had been 'shortened' by 11 days! If you want to know how many days have passed since that big switch, by the way, give our days between dates calculator a try. (Source: www.thecalculatorsite.com)

 

 

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