To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

Common year starting on Thursday

From Wikipedia, the free encyclopedia

A common year starting on Thursday is any non-leap year (i.e. a year with 365 days) that begins on Thursday, 1 January, and ends on Thursday, 31 December. Its dominical letter hence is D. The most recent year of such kind was 2015 and the next one will be 2026 in the Gregorian calendar[1] or, likewise, 2021 and 2027 in the obsolete Julian calendar, see below for more.

This is the only common year with three occurrences of Friday the 13th: those three in this common year occur in February, March, and November. Leap years starting on Sunday share this characteristic, for the months January, April and July. From February until March in this type of year is also the shortest period (one month) that runs between two instances of Friday the 13th. Additionally, this is the one of only two types of years overall where a rectangular February is possible, in places where Sunday is considered to be the first day of the week. Common years starting on Friday share this characteristic, but only in places where Monday is considered to be the first day of the week.

YouTube Encyclopedic

  • 1/5
    Views:
    4 744 069
    1 918 741
    989
    1 054 991
    721
  • What is a Leap Year?
  • Why Do We Have LEAP YEARS? | What Is A LEAP YEAR? | The Dr Binocs Show | Peekaboo Kidz
  • Counting the Number of Wednesdays and Leap Year Struggle
  • What Is a Leap Year?
  • To check leap year in python programming ( python for beginners )

Transcription

A calendar year is made of three hundred and sixty five days -- a number that refuses to be divide nicely, which is why we end up with uneven months of either 30 or 31 days. Except for February -- the runt of the litter -- which only gets 28... except when it gets 29 and then the year is 366 days long. Why does that happen? What kind of crazy universe do we live in where some years are longer than others? To answer this we need to know: just what is a year? Way oversimplifying it: a year is the time it takes Earth to make one trip around the sun. This happens to line up with the cycle of the seasons. Now, drawing a little diagram like this showing the Earth jauntily going around the sun is easy to do, but accurately tracking a year is tricky when you're on Earth because the universe doesn't provide an overhead map. On Earth you only get to see the seasons change and the obvious way to keep track of their comings and goings is to count the days passing which gives you a 365 day calendar. But as soon as you start to use that calendar, it slowly gets out of sync with the seasons. And with each passing year the gap gets bigger and bigger and bigger. In three decades the calendar will be off by a week and in a few hundred years the seasons would be flipped -- meaning Christmas celebrations taking place in summer -- which would be crazy. Why does this happen? Did we count the days wrong? Well the calendar predicts that the time it takes for the Earth to go around the sun is 8,760 hours. But, if you actually timed it with a stopwatch you'd see that a year is really longer than the calendar predicts by almost six hours. So our calendar is moving ever-so-slightly faster than the seasons actually change. And thus we come to the fundamental problem of all calendars: the day/night cycle, while easy to count, has nothing to do with the yearly cycle. Day and night are caused by Earth rotating about its axis. When you're on the side faceing the sun, it's daytime and when you're on the other side it's night. But this rotation is no more connected to the orbital motion around the sun than a ballerina spinning on the back of a truck is connected to the truck's crusing speed. Counting the number of ballerina turns to predict how long the truck takes to dive in a circle might give you a rough idea, but it's crazy to expect it to be precise. Counting the days to track the orbit is pretty much the same thing and so it shouldn't be a surprise when the Earth dosen't happen to make exactly 365 complete spins in a year. Irritatingly, while 365 days are too few 366 days are too many and still cause the seasons to drift out of sync, just in the opposite way. The solution to all this is the leap year: where February gets an extra day, but only every four years. This works pretty well, as each year the calendar is about a quarter day short, so after four years you add an extra day to get back in alignment. Huzzah! The problem has been solved. Except, it hasn't. Lengthening the calendar by one day every four years is slightly too much, and the calendar still falls behind the seasons at the rate of one day per hundred years. Which is fine for the apathetic, but not for calendar designers who want everything to line up perfectly. To fix the irregularity, every century the leap year is skipped. So 1896 and 1904 were leap years but 1900 wasn't. This is better, but still leaves the calendar ever-so-slightly too fast with an error of 1 day in 400 years. So an additional clause is added to the skip the centuries rule that if the century is divisible by 400, then it will be a leap year. So 1900 and 2100 aren't leap years, but 2000 is. With these three rules, the error is now just one day off in almost eight thousand years which the current calendar declares 'mission accomplished' and so calls it a day. Which is probably quite reasonable because eight thousand years ago humans were just figuring out that farming might be a good idea and eight thousand years from now we'll be hopefully be using a calendar with a better date tracking system. But perhaps you're a mathematician and a 0.0001 percent error is an abomination in your eyes and must be removed. "Tough luck" says The Universe because the length of a day isn't even constant. It randomly varies by a few milliseconds and on average and very slowly decreases by about 1 millisecond per hundred years. Which means it's literally impossible to build a perfect calendar that lasts forever. In theory the length of a day will expand to be as long as a curent month -- but don't worry in practice it will take tens of billions of years, and our own expanding sun will destroy the earth long before that happens. Sorry, not quite sure how we got from counting the days of the months to the fiery unavoidable end of all human civilization -- unless of course we have an adequately funded space program (hint, hint) -- but there you have it. For the next eight millennia Leap years will keep the calendar in sync with the seasons but in a surprisingly complicated way. You can learn a lot more about orbits, different kinds of years and supermassive black holes and over at Minute Physics. As always, Henry does a great job of explaining it all in his new video. Check it out.�

Calendars

Calendar for any common year starting on Thursday,
presented as common in many English-speaking areas
January
Su Mo Tu We Th Fr Sa
01 02 03
04 05 06 07 08 09 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
 
February
Su Mo Tu We Th Fr Sa
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
 
 
March
Su Mo Tu We Th Fr Sa
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31  
 
April
Su Mo Tu We Th Fr Sa
01 02 03 04
05 06 07 08 09 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30  
 
May
Su Mo Tu We Th Fr Sa
01 02
03 04 05 06 07 08 09
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31  
June
Su Mo Tu We Th Fr Sa
01 02 03 04 05 06
07 08 09 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30  
 
July
Su Mo Tu We Th Fr Sa
01 02 03 04
05 06 07 08 09 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31  
 
August
Su Mo Tu We Th Fr Sa
01
02 03 04 05 06 07 08
09 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31  
September
Su Mo Tu We Th Fr Sa
01 02 03 04 05
06 07 08 09 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30  
 
October
Su Mo Tu We Th Fr Sa
01 02 03
04 05 06 07 08 09 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
 
November
Su Mo Tu We Th Fr Sa
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30  
 
December
Su Mo Tu We Th Fr Sa
01 02 03 04 05
06 07 08 09 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31  
 
ISO 8601-conformant calendar with week numbers for
any common year starting on Thursday (dominical letter D)
January
Wk Mo Tu We Th Fr Sa Su
01 01 02 03 04
02 05 06 07 08 09 10 11
03 12 13 14 15 16 17 18
04 19 20 21 22 23 24 25
05 26 27 28 29 30 31  
   
February
Wk Mo Tu We Th Fr Sa Su
05 01
06 02 03 04 05 06 07 08
07 09 10 11 12 13 14 15
08 16 17 18 19 20 21 22
09 23 24 25 26 27 28
   
March
Wk Mo Tu We Th Fr Sa Su
09 01
10 02 03 04 05 06 07 08
11 09 10 11 12 13 14 15
12 16 17 18 19 20 21 22
13 23 24 25 26 27 28 29
14 30 31  
April
Wk Mo Tu We Th Fr Sa Su
14 01 02 03 04 05
15 06 07 08 09 10 11 12
16 13 14 15 16 17 18 19
17 20 21 22 23 24 25 26
18 27 28 29 30  
   
May
Wk Mo Tu We Th Fr Sa Su
18 01 02 03
19 04 05 06 07 08 09 10
20 11 12 13 14 15 16 17
21 18 19 20 21 22 23 24
22 25 26 27 28 29 30 31
   
June
Wk Mo Tu We Th Fr Sa Su
23 01 02 03 04 05 06 07
24 08 09 10 11 12 13 14
25 15 16 17 18 19 20 21
26 22 23 24 25 26 27 28
27 29 30  
   
July
Wk Mo Tu We Th Fr Sa Su
27 01 02 03 04 05
28 06 07 08 09 10 11 12
29 13 14 15 16 17 18 19
30 20 21 22 23 24 25 26
31 27 28 29 30 31  
   
August
Wk Mo Tu We Th Fr Sa Su
31 01 02
32 03 04 05 06 07 08 09
33 10 11 12 13 14 15 16
34 17 18 19 20 21 22 23
35 24 25 26 27 28 29 30
36 31  
September
Wk Mo Tu We Th Fr Sa Su
36 01 02 03 04 05 06
37 07 08 09 10 11 12 13
38 14 15 16 17 18 19 20
39 21 22 23 24 25 26 27
40 28 29 30  
   
October
Wk Mo Tu We Th Fr Sa Su
40 01 02 03 04
41 05 06 07 08 09 10 11
42 12 13 14 15 16 17 18
43 19 20 21 22 23 24 25
44 26 27 28 29 30 31  
   
November
Wk Mo Tu We Th Fr Sa Su
44 01
45 02 03 04 05 06 07 08
46 09 10 11 12 13 14 15
47 16 17 18 19 20 21 22
48 23 24 25 26 27 28 29
49 30  
December
Wk Mo Tu We Th Fr Sa Su
49 01 02 03 04 05 06
50 07 08 09 10 11 12 13
51 14 15 16 17 18 19 20
52 21 22 23 24 25 26 27
53 28 29 30 31  
   

Applicable years

Gregorian Calendar

In the (currently used) Gregorian calendar, alongside Tuesday, the fourteen types of year (seven common, seven leap) repeat in a 400-year cycle (20871 weeks). Forty-four common years per cycle or exactly 11% start on a Thursday. The 28-year sub-cycle only spans across century years divisible by 400, e.g. 1600, 2000, and 2400.

This type of year has 53 weeks in the week-day format of the ISO 8601 standard.

Gregorian common years starting on Thursday[1]
Decade 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th
16th century prior to first adoption (proleptic) 1587 1598
17th century 1609 1615 1626 1637 1643 1654 1665 1671 1682 1693 1699
18th century 1705 1711 1722 1733 1739 1750 1761 1767 1778 1789 1795
19th century 1801 1807 1818 1829 1835 1846 1857 1863 1874 1885 1891
20th century 1903 1914 1925 1931 1942 1953 1959 1970 1981 1987 1998
21st century 2009 2015 2026 2037 2043 2054 2065 2071 2082 2093 2099
22nd century 2105 2111 2122 2133 2139 2150 2161 2167 2178 2189 2195
23rd century 2201 2207 2218 2229 2235 2246 2257 2263 2274 2285 2291
24th century 2303 2314 2325 2331 2342 2353 2359 2370 2381 2387 2398
25th century 2409 2415 2426 2437 2443 2454 2465 2471 2482 2493 2499
400-year cycle
0–99 9 15 26 37 43 54 65 71 82 93 99
100–199 105 111 122 133 139 150 161 167 178 189 195
200–299 201 207 218 229 235 246 257 263 274 285 291
300–399 303 314 325 331 342 353 359 370 381 387 398

Julian Calendar

In the now-obsolete Julian calendar, the fourteen types of year (seven common, seven leap) repeat in a 28-year cycle (1461 weeks). A leap year has two adjoining dominical letters (one for January and February and the other for March to December, as 29 February has no letter). This sequence occurs exactly once within a cycle, and every common letter thrice.

As the Julian calendar repeats after 28 years that means it will also repeat after 700 years, i.e. 25 cycles. The year's position in the cycle is given by the formula ((year + 8) mod 28) + 1). Years 3, 14 and 20 of the cycle are common years beginning on Thursday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Thursday.

Julian common years starting on Thursday
Decade 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th
15th century 1405 1411 1422 1433 1439 1450 1461 1467 1478 1489 1495
16th century 1506 1517 1523 1534 1545 1551 1562 1573 1579 1590
17th century 1601 1607 1618 1629 1635 1646 1657 1683 1674 1685 1691
18th century 1702 1713 1719 1730 1741 1747 1758 1769 1775 1786 1797
19th century 1803 1814 1825 1831 1842 1853 1859 1870 1881 1887 1898
20th century 1909 1915 1926 1937 1943 1954 1965 1971 1982 1993 1999
21st century 2010 2021 2027 2038 2049 2055 2066 2077 2083 2094

Holidays

International

Roman Catholic Solemnities

Australia and New Zealand

British Isles

Canada

United States

References

  1. ^ a b Robert van Gent (2017). "The Mathematics of the ISO 8601 Calendar". Utrecht University, Department of Mathematics. Retrieved 20 July 2017.
This page was last edited on 15 March 2024, at 20:34
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.