What years are leap years? How do I find the day of the week for any date?

Answer 1

It takes the earth about 365.2422 days to go around the sun, but a normal calendar year is only 365 days. The extra fraction of a day adds up: circling the sun four times takes 1460.9688 days, but four calendar years would only be 1460 days. That .9688 is almost a whole day, so every four years we add an extra day to our calendar, February 29. We call that year leap year. To make things easier, leap years are always divisible by four: 2004 and 2008 will both be leap years.

For hundreds of years, people used a calendar called the Julian calendar that followed this rule, adding a leap year every four years. However, because .9688 isn't exactly a whole day, the Julian calendar slowly began to disagree with the real seasons. In 1582, Pope Gregory fixed this problem by ordering everyone to use a new set of rules. These rules are named the Gregorian calendar, after him. They work like this:

The Gregorian Calendar Rule Examples
Every fourth year is a leap year. 2004, 2008, and 2012 are leap years.
However, every hundredth year is not a leap year. 1900 and 2100 are not leap years.
Every four hundred years, there's a leap year after all. 2000 and 2400 are leap years.

People in English-speaking countries didn't start using the Gregorian calendar until 1752. Some countries, such as Iran, still use other systems.

What day of the week will it be, a year from today?

Suppose that today is February 13, 2053. The day of the week is a Thursday. One week (seven days) from today, on February 20, 2053, it will be Thursday again. After two weeks (fourteen days), it will be Thursday once more. We need to figure out how many weeks and days will have passed after a year. 2053 is not a leap year, so 365 days will pass between February 13, 2053 and February 13, 2054. Let's divide by 7 to find out how many weeks that is: 365 / 7 = 52, remainder 1, or fifty-two weeks with one day left over. Fifty-two weeks after February 13, 2053 is yet another Thursday, so fifty-two weeks and one day later must be a Friday.

We can use the same method for any date, but we have to be careful. Because some years are leap years, a year from today might be 366 days and not 365. For instance, there are 366 days between Saturday, November 20, 2055 and November 20, 2056, because 2056 is a leap year and February 29, 2056 lies between the two Novembers..

Answer 2

Leap years are those years in which we have one extra day as compared to an ordinary yr.
It has 366 days instead of 365.

....Leap years occur after time of every 4 yrs n thus are divisible by 4!
Last leap yr occurred in 2004 n will come again in 2008 n after that in 2012 n so on.......

U can find the day of the week for any date by first adding 7 to the current date
like if it is 16 today then it'll be 23 on the next Friday
or if u want to know wat will be the day after three days simply add 3 to the crnt date and u will find that it will be 19 after 3 days.
now when u have find the date simply move to the boxes or partitions of ur fingers and supposing that 1st box is Sunday, 2nd box is Monday n so on n the 7th one Saturday........ u can find the day by counting it (16th date) from 6th box of ur finger which is for Friday n then moving to 7th box which is for Saturday (17th date) n then again skipping to the 1st box for Monday (18th date) n then finally to the (19th date) 2nd box for Tuesday, (which u were to find)

It is appearing lengthy theoretically but very short n easy to use practically!!!!!!

GOD Bless!!!!!!!!

Answer 3

quite it extremely is extremely elementary to detect the day of the week with out finding on the calendar.first of all all the years divisible by 4 are bounce years different than if the three hundred and sixty 5 days is divisible by one hundred.yet returned all the years divisible by 4 hundred are bounce years. coming to the thank you to outline the day, in basic terms upload up all the days upto that day ex. 14/one million/1991 all the days upto this date from the 1st day of the millineum i. e. 01/01/0001. yet another extra straightforward technique is that overlook approximately all the years that are divisible by 4 hundred like 1200 1600 2000 etcu do no longer could count style the days till those some years in basic terms initiate from day after immediately of those years.(do no longer overlook the bounce years) then divide the no of days by 7 and the rest tells u the day. if the rest is 0 then it extremely is a sunday one million monday 2 tuesday....................6 saturday.locate out and characteristic relaxing

Answer 4

Leap year is any year on or after 1600 evenly divisible by 400, or evenly divisible by 4 and not 100.

For day of week, look at the source I provide.

Answer 5

well a leap year occurs every four years and they years are usually divisible by four like 2008 2004 2012 and i dont understand you second question...maybe this site will help..

http://en.wikipedia.org/wiki/Leap_year

Answer 6

There are methods for doing this calculation: http://userpages.wittenberg.edu/bshelburne/Comp150/DayOfWeek.htm

But I'd just find an online source like this one:

http://www.searchforancestors.com/utility/dayofweek.html

Answer 7

A leap year (or intercalary year) is a year containing an extra day (or, in case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. For example, February would have 29 days instead of just 28. Seasons and astronomical
This graph shows the variation between the seasonal year versus the calendar year due to unequally spaced 'leap days' rules. See Iranian calendar to contrast with a calendar based on 8 leap days every 33 years.

Leap year rules

In order to get a closer approximation, it was decided to have a leap day 97 years out of 400 rather than once every four years. To implement the model, it was provided that years divisible by 100 would be leap years only if they were divisible by 400 as well. [2] [3] So, in the last millennium, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. In this millennium, 2100, 2200, 2300, 2500, 2600, 2700, 2900 and 3000 will not be leap years, but 2400 and 2800 will be. The years that are divisible by 100 but not 400 are known as "exceptional common years". By this rule, the average number of days per year will be 365 + 1/4 - 1/100 + 1/400 = 365.2425.
Leap Year Algorithms

Standard:

if year mod 400 eq 0 then leap
else if year mod 100 eq 0 then no_leap
else if year mod 4 eq 0 then leap
else no_leap


Vectorized:

mask400 = year mod 400 EQ 0 ; this is a leap year
mask100 = year mod 100 EQ 0 ; these are not leap years
mask4 = year mod 4 EQ 0 ; this is a leap year
return mask4 and (~mask100 or mask400)

where ~ is the bitwise logical NOT operator

Leap day

The Gregorian calendar is a modification of the Julian calendar first used by the Romans. The Roman calendar originated as a lunisolar calendar and named many of its days after the syzygies of the moon: the new moon (Kalendae or calends, hence "calendar") and the full moon (Idus or ides). The Nonae or nones was not the first quarter moon but was exactly one nundinae or Roman market week of nine days before the ides, inclusively counting the ides as the first of those nine days. In 1825, Ideler believed that the lunisolar calendar was abandoned about 450 BC by the decemvirs, who implemented the Roman Republican calendar, used until 46 BC. The days of these calendars were counted down (inclusively) to the next named day, so 24 February was ante diem sextum Kalendae Martii ("the sixth day before the calends of March") often abbreviated a. d. VI Kal. Mar. The Romans counted days inclusively in their calendars, so this was actually the fifth day before March 1 when counted in the modern exclusive manner (not including the starting day).[4]

The Republican calendar's intercalary month was inserted immediately after Terminalia (a. d. VII Kal. Mar., February 23) or immediately after Regifugium (a. d. VI Kal. Mar., February 24). This intercalary month, named Intercalaris or Mercedonius, contained 27 days, 22 additional days to which the last five days of February were added. Because only 22 or 23 days were effectively added, not a full lunation, the calends and ides of the Roman Republican calendar were no longer associated with the new moon and full moon.

When Julius Caesar developed the Julian calendar in 46 BC, becoming effective in 45 BC, in addition to distributing an extra ten days among the months of the Roman Republican calendar he replaced the intercalary month by a single intercalary day, located where the intercalary month used to be. To create the intercalary day, the existing ante diem sextum Kalendae Martii (February 24) was doubled, hence the year containing the doubled day was a bissextile (twice sixth) year. Which of the two days was the intercalary day and which was the ordinary day is moot. Apparently the second half was originally regarded as the intercalary day, but in 238 Censorinus stated that the intercalary day was followed by the last five days of February, a. d. VI, V, IV, III and pridie Kal. Mar. (which would be those days numbered 24, 25, 26, 27, and 28 from the beginning of February in a common year), hence he regarded the bissextum as the first half of the doubled day. All later writers, including Macrobius about 430, Bede in 725, and other medieval computists (calculators of Easter), continued to state that the bissextum (bissextile day) occurred before the last five days of February.

Until quite recently, the Roman Catholic Church always celebrated the feast of Saint Matthias on a. d. VI Kal. Mar., so if the days were numbered from the beginning of the month, it was named February 24 in common years, but the presence of the bissextum in a bissextile year immediately before a. d. VI Kal. Mar. shifted the latter day to February 25 in leap years.

Julian, Coptic and Ethiopian Calendars

The Julian calendar adds an extra day to February in years evenly divisible by four.

The Coptic calendar and Ethiopian calendar also add an extra day to the end of the year once every four years before a Julian 29-day February.

This rule gives an average year length of 365.25 days. However, it was 11 minutes longer than a real year. This means that the vernal equinox moves a day earlier in the calendar every 131 years.

Revised Julian Calendar

The Revised Julian calendar adds an extra day to February in years divisible by four, except for years divisible by 100 that do not leave a remainder of 200 or 600 when divided by 900. This rule agrees with the rule for the Gregorian calendar until 2799. The first year that dates in the Revised Julian calendar will not agree with the those in the Gregorian calendar will be 2800, because it will be a leap year in the Gregorian calendar but not in the Revised Julian calendar.

This rule gives an average year length of 365.242222… days. This is a very good approximation to the mean tropical year, but because the vernal equinox year is slightly longer, the Revised Julian calendar does not do as good a job as the Gregorian calendar of keeping the vernal equinox on or close to 21 March.

Chinese calendar

The Chinese calendar is lunisolar, so a leap year has an extra month, often called an embolismic month after the Greek word for it. In the Chinese calendar the leap month is added according to a complicated rule, which ensures that month 11 is always the month that contains the northern winter solstice. The intercalary month takes the same number as the preceding month; for example, if it follows the second month (二月) then it is simply called "leap second month" (Traditional Chinese: 閏二月; Simplified Chinese: 闰二月; pinyin: rùn'èryuè).
Hebrew calendar

The Hebrew calendar is also lunisolar with an embolismic month. This extra month is called Adar Alef (first Adar) and is added before Adar, which then becomes Adar bet (second Adar). According to the Metonic cycle, this is done seven times every nineteen years, specifically, in years 3, 6, 8, 11, 14, 17, and 19.

In addition, the Hebrew calendar has postponement rules that postpone the start of the year by one or two days. These postponement rules reduce the number of different combinations of year length and starting days of the week from 28 to 14, and regulate the location of certain religious holidays in relation to the Sabbath. In particular, the first day of the Hebrew year can never be Sunday, Wednesday or Friday. This rule is known in Hebrew as "lo adu rosh", i.e. "Rosh [ha-Shanah] is not Sunday, Wednesday or Friday" (as the Hebrew word adu is written by three Hebrew letters signifying Sunday, Wednesday and Friday). Accordingly, the first day of Pesah is never Monday, Wednesday or Friday. This rule is known in Hebrew as "lo badu Pesah", which has a double meaning - "Pesah is not a legend", but also "Pesah is not Monday, Wednesday or Friday" (as the Hebrew word badu is written by three Hebrew letters signifying Monday, Wednesday and Friday).

One reason for this rule is that Yom Kippur, the holiest day in the Hebrew calendar, must never be adjacent to the weekly Sabbath (which is Saturday), i.e. it must never fall on Friday or Sunday, in order not to have two adjacent Sabbath days (Yom Kippur can be on Saturday, however).

Calendars with Leap Years synchronized with Gregorian

The Indian National Calendar and the Revised Bangla Calendar of Bangladesh organise their leap years so that the leap day is always close to February 29 in the Gregorian calendar. This makes it easy to convert dates to or from Gregorian.

The Bahá'í calendar is structured such that the leap day always falls within Ayyám-i-Há, a period of four or five days corresponding to Gregorian February 26 - March 1. Because of this, Baha'i dates consistently line up with exactly one Gegorian date.

Hindu Calendar

In the Hindu calendar, which is a lunisolar calendar, the embolismic month is called adhika maas (extra month). It is the month in which the sun is in the same sign of the stellar zodiac on two consecutive dark moons.

[edit] Iranian calendar

The Iranian calendar also has a single intercalated day once in every four years, but every 33 years or so the leap years will be five years apart instead of four years apart. The system used is more accurate and more complicated, and is based on the time of the March equinox as observed from Tehran. The 33-year period is not completely regular; every so often the 33-year cycle will be broken by a cycle of 29 or 37 years.

Long term leap year rules

The accumulated difference between the Gregorian calendar and the vernal equinoctial year amounts to 1 day in about 8,000 years. This suggests that the calendar needs to be improved by another refinement to the leap year rule: perhaps by avoiding leap years in years divisible by 8,000.

(The most common such proposal is to avoid leap years in years divisible by 4,000 [1]. This is based on the difference between the Gregorian calendar and the mean tropical year. Others claim, erroneously, that the Gregorian calendar itself already contains a refinement of this kind [2].)

A system of 128-year-based leap years has been proposed, and it can be adopted directly without any modification to current leap year calculations until the year 2048.

However, there is little point in planning a calendar so far ahead because over a timescale of tens of thousands of years the number of days in a year will change for a number of reasons, most notably:

1. Precession of the equinoxes moves the position of the vernal equinox with respect to perihelion and so changes the length of the vernal equinoctial year.
2. Tidal acceleration from the sun and moon slows the rotation of the earth, making the day longer.

In particular, the second component of change depends on such things as post-glacial rebound and sea level rise due to climate change. We can't predict these changes accurately enough to be able to make a calendar that will be accurate to a day in tens of thousands of years.

Marriage proposal

There is a tradition, said to go back to Saint Patrick and Saint Bridget in 5th century Ireland, but apparently not attested before the 19th century, whereby women may make marriage proposals only in leap years.

Supposedly (but disputed), in a 1288 law by Queen Margaret of Scotland (then age five and living in Norway), fines were levied if the proposal was refused by the man; compensation ranged from a kiss to £1 to a silk gown, in order to soften the blow.[5] Because men felt that put them at too great a risk, the tradition was in some places tightened to restricting female proposals to 29 February.

Others regard these supposed folk traditions as unhistorical.

Birthdays

A person born on February 29 may be called a "leapling". In common years they usually celebrate their birthdays on 28 February or 1 March.

For legal purposes, their legal birthdays depend on how different laws count time intervals. In Taiwan, for example, the legal birthday of a leapling is 28 February in common years, so a Taiwanese leapling born on February 29, 1980 would have legally reached 18 years old on February 28, 1998.
“ If a period fixed by weeks, months, and years does not commence from the beginning of a week, month, or year, it ends with the ending of the day which proceeds the day of the last week, month, or year which corresponds to that on which it began to commence.　But if there is no corresponding day in the last month, the period ends with the ending of the last day of the last month.”

There are many instances in children's literature where a person's claim to be only a quarter of their actual age turns out to be based on counting their leap-year birthdays. A similar device is used in the plot of the Gilbert and Sullivan operetta The Pirates of Penzance.