Some very gifted people are able to calculate the day of the week for any date in their heads quickly and precisely.There are a number of ways to make this calculation.

Step 1: The value for the month should be added with the day.

The highest multiple of 7 is subtracted if the number is greater than 6.Hold this number.

Step 2: The year that has the highest multiple of 28 is the last two digits.

Add to the number you get when you divide it by 4 and round it down.The Century Table has a value for the Century.If the month is January or February, subtract 1

Step 3: The results from the previous steps should be added.

The highest multiple of 7 is subtracted if the number is greater than 6.Look up the day of the week in the Weekday-Table using the resulting number.The table has year value.As shown in the table by the 0 for century 2000, the four-number cycle repeats itself indefinitely.The 3300s had a value of 5.The difference between the two digit century and the highest multiple of 4 in it can be used to calculate the value.When reduced by the 7s in it, the 3400s are equal to 3.This formula could be extended further to encompass and compute the entire Year value in one felled swoop, but that formula, at its simplest, would be too complicated to carry around in your head and then perform the calculation quickly and precisely, which are the goals of the process explained here.This process can be used to find the month, day, or year if any one of them is missing, but the Day-of-the-Week is known.

Step 4: "Wednesday" and "2007" should be remembered.

Your base day is this one.The day of the week will be calculated using the instructions below.How to move this to other years will be shown in the final steps.

Step 5: Pick out the following dates.

They are all Wednesdays in 2007, starting on April 4 and ending on December 12.The symmetry makes these easy to remember for Americans and Europeans.The people at the 7/11 work from 9 to 5, and reverse the numbers as well.You will have 1 day-of-week from April to December.January, February, and March have their base days on Wednesday.It's 7,14,21,28 and we're doing math by 7s because there are 7 days per week.Every month you have 1 day-of-week.You should be able to easily calculate the day-of-week for any date in 2007.

Step 6: If you want to use this for other years, increase your day by one for each year.

Step 7: For the month of January and February, calculate as usual.

For March and beyond, add an extra day for other months.

Step 8: Every day of the year, assign a letter to the alphabet.

We use seven letters since there are seven days in a week.January 1 is A, January 2 is B, and so on.It begins from A again after G.January 8 will be A again since January 7 is G.

Step 9: Continue through the entire year this way.

We are ignoring leap years for now.We will be back at the letter A for fifty-third time when we reach December 31.There is a chart of day letters.,---,Jan, Feb, Mar,Apr, Jul,Aug,Sep,Oct,Nov, Dec.

Step 10: The Sunday Letter is a self-explanatory term for the year you care about.

The Sunday Letter in 2005 is B.In 2006 it is A.It is G for 2007, back one letter from the year before.The Sunday Letter is F for January and February due to the leap day.The Sunday Letter is E for March through December and D for the rest of the year.Here is the whole table.,1600,1700,1800,1900.C, E, G, B, D, and BA all have the same number of days.1600,1700,1800,1900,2000 to 2200 and 2300.Is it possible that it is.

Step 11: To find the day of the week, put these together.

Let's try June 2007, for example.The day table shows that June 3 is G and therefore a Sunday.We wanted to know what happened on June 4.June 4 is the day after June 3.June 4, 2007, is a Monday.

Step 12: If you need help, you can use the info below.

Is this the first one?

Step 13: A long time.

With the exception of years that are 100 and 400, they are not leap years.The guide refers to non-leap years as normal years.The Gregorian calendar has been reformed in the past and only applies to the most recent state.The "Julian calendar" section of the Wikipedia article entitled "Doomsday rule" gives more information on this reform and its consequences.B.C.E. will be used in this guide.Refer to the article entitled "Common Era" for more information.Think of C.E.As positive and B.C.E. years.subtract one from them first to make them negative years.Think of 1670 C.E.Think of 1540 B.C.E. as 1670.As -1539.If you want to place a negative sign in front of it, you have to subtract 1 from 1540 because there is no year 0 in the Gregorian calendar.The article entitled "Astronomical year numbering" is a more detailed explanation.The formats are used to represent dates in a compact form.For example, 8/6 is equivalent to August 6th, 7/24-1670, 12/6/534, and 10/23/-1889.It requires very little knowledge of addition, subtraction, multiplication, and division and can be very fast with practice.John Horton Conway, a renowned mathematics professor atPrinceton University, took up day-of-the-week calculation as a hobby and developed the Doomsday Algorithm.He was able to calculate the day of the week in his head for any day on the Gregorian calendar in 3 seconds.If you doubt that the algorithm can be performed quickly, watch this performance by Arthur T. Benjamin, the "Mathemagician" and a math professor at Harvey Mudd College.One of his later tricks is the day-of-the-week calculation.You can improve your speed with practice, even if you've never met someone who is that fast.A branch of mathematics known as modular arithmetic is used in the Doomsday Algorithm.Similar tricks could be developed for any calendar system.The guide doesn't assume a mathematical background; instead, it should be read in conjunction with the Advanced Tricks for Greater Speed section of the guide.Feel free to skip the examples if you already understand the concepts they show.If you don't know how the days of the week were calculated, you should not be concerned.If you already understand some of the subtler concepts, you may want to skim over them.

Step 14: It was months.

There are 31 days in January, March, May, July, August, and October.There are 30 days in April, June, September and November.During a normal year, February has 28 days and 29 days during a leap year.February 29 is the only day that a leap year exists.It is possible to distinguish between months with 31 days and less.Hold out your right hand.January has more days than February because your knuckle is taller than the gap between your index and middle fingers.All of the months with 31 days are on knuckles, while the other months are in gaps.You are probably wondering what to do once you get to July.To get to the rest of the months, tap the knuckle of your index finger again and say "August."

Step 15: There were days.

Every year, the days of doom are on the same day of the week.There are a number of easy-to-remember Doomsdays.In the year 2000, for example, April 4, June 6, July 11, and November 7 are all Tuesdays, and there is a 9 to 5 job at a 7-11 gas station.This does not mean that April 4, 2001 was also Tuesday.April 4, 2001 was a Wednesday.If you add or subtract 7 from any Doomsday, you can get another one.For example, 5/9, 5/16, and 5/23 are all dooms.You don't have to add or subtract 7 at a time, you can use any multiple of 7.9/6 and 9/26 are both Doomsdays, because of 5+7*3 26.It's easy to remember that Doomsday is 3/0.3/0 is a way of thinking about the last day of February.Regardless of whether or not it is a leap year, 3/0 is always the last day of February.The world can see months as having negative days.Both 8/7 and 8/6 are considered to be Doomsdays.Simply add the number of days in the 7th month to convert 8/ 6 into a normal date.The knuckle trick can be used to determine if there are 31 days in July.8/6 is the same as 7/25.We can think of months as having days greater than 31.Both 10/10 and 10/34 are apocalypses.Simply subtract the number of days in the 10th month to convert 10/34 into a normal date.October has 31 days, so 10/34 is 11/3 and 34-31 3.We can write June days as March days.For example, 6/6 and 6/64 are the most dangerous.The month of May has 31 days.There are 30 days in the month of April.March has 31 days, so 4/-2 and 3/28.June -64th is equivalent to March 28th.It is important to account for leap years when determining Doomsdays in January or February.In a leap year February has 29 days, so 3/-14 2/15, but in a normal year it has 28 days.During leap years, February 15th is a Doomsday, but in normal years it is February 14th.It's important to be careful when going from March to January.The normal year is 3/-42 2/-14.

Step 16: You can use your knowledge of the Gregorian calendar now that you know how it works.

Number-days are numbers that are associated with days of the week.Monday is one day, Tuesday is two days, and Wednesday is three days.Sunday is both 0 and 7.It could be thought of as -8, 71, etc.Congruity symbols,, rather than equals signs, are equivalent to determine the day of the week because 71 does not equal 8.We only look at the rest of the week when the numbers are divided by 7.The numbers are congruent if their remainders are the same when they are divided by 7.The earlier point is that you can add or subtract multiples of 7 as you please.For example, 1 8 and 8 are the same.There are more examples of how modulo behaves.All congruences are assumed to be modulo 7, so the notation "(mod 7)" will be left off the guide.If you know that August 8, 1953, is a Saturday, then you can quickly determine that the day is Tuesday.That is, 6-3.If you know that 9/7/1776 is a SIXAday, then you can see that it is because of 7 and 6.You can add or subtract multiples of 7 to a Number-day.If you know that 10/2/ 2543 is a five day week, then you can quickly determine that.Remember to watch out for leap years, like 18,400.If you know that 2/28/18,400 is a single day, then you can determine the number of days in a row.

Step 17: There are two definitions of year days and century days.

Every year, the "Year-day" is the day of the week on which all of its doomsdays lie.The Year-day of 2009, for example, is Saturday.The first year of the century is known as the Year-day.The first year of a century is called the Century-year.The Century-day of the 1900s is Wednesday.The 20th century is Wednesday.The Century-year of the 20th century is 1900.There is a Century-year of the century that lies in.The -1400s or the 14th century B.C.E.It's not -1300 because -1400 comes before it.It's important to remember that -1400 is not the same as 1401 B.C.E.

Step 18: Calculating big Tuesdays for 400 years.

Tuesday is the year-day of every year.The Year-days are called Big Tuesdays to help you remember them.The Year-day of 1600 is a Big Tuesday because it is the 400th day of the year.The Century-days of the 2000s, the -4400s and the 96,812,000s are all Big Tuesdays.

Step 19: Calculating century days

The Century-day can be found if you are not in a Big Tuesday-century.When you get to a Big Tuesday-year, subtract 100.How many times did you subtract 100?One of every four Century-years is a Big Tuesday-year, so you messed up if you subtracted 100 once.The Century-day of the 1800s is Friday because you subtract 100 twice to get 1600, which is a Big Tuesday-year.The pattern is 1600, 2, 1700, Sunday, 0, 1800, 5, and 1900.By subtracting two from the initial Century-day, you can get from one day to the next.When the larger of the two adjacent centuries is not a Big Tuesday-century, this works.You already know that the Century-day of every Big Tuesday-century is two days.

Step 20: It takes 12 years to calculate Dozen-days.

The largest year that is less than or equal to the previous year is called the Dozen-year and it has the same property as the Century- year.The Year-day of the Dozen-year is the "Dozen- day" of any given year.Adding the Century-day to the result of the division will calculate the Dozen-Day.There is a positive difference between the Dozen-year of 1234 and the larger years that are still less than or equal to it.The Year-day of 1224 is Thursday.The Dozen-days for 1235, 1226, and 1229 are on Thursdays as well as Fridays.The Dozen-day of 1713 can be calculated.The Century-day of the -1700s is what we need to find.To arrive at a Big Tuesday-year, we must subtract 100 three times.We must find a year.The Dozen-year is not -1712 but -1816, because of the number 84.Since we can subtract 7 as we please, the day is three days long.

Step 21: Calculating four days in a row.

The greatest number that is less than or equal to the given year is the Quad-year.The Year-day of the Quad-year is any given day.The Quad-year of 1620 is 1620.The Quad-days of 1640, 1641,1642, and 1643 are all Wednesday.The Quad-day can be calculated as follows.The year 1642 is the Dozen-year because of 1636-1600 12*3.The Century-year, 1600, is a big day.The Dozen-day of 1642 is Friday.Take 4 from the Quad-year, 1640, until you get to the Dozen- year.Add the number of times you subtracted by -2 to get the Quad-day.The Quad-day of 1642 is Wednesday in our example.It is the Year-day of 1640 on Wednesday.

Step 22: Calculating the number of days in a year.

If 1642 is not divisible by 4, then subtract the Quad-year from the given year.To get the Year-day, add the result to the Quad- day.The Year-day of 1642 is Friday.

Step 23: Calculating the number of days and months in a year.

You know the day of the week of every Doomsday once you know Year-day.If the date was 9/5/1642, you would know that it was a Friday.You would have to subtract 7 days to find out that the same day of the week is 6/6/1642, which is a known Doomsday.This means that 6/20/1642 is a Friday.

Step 24: The days of the week are calculated.

If you are given a date like 4/20/1642, which is not a Doomsday, you can simply find the nearest one by adding or subtracting 7.We add 14 days to discover that 4/18/1642 is a Doomsday.We can add 2 days to find out that 4/20/1642 is a SE'enday.There is a chance that the nearest known Doomsday may not be in the same month.3/0/1642 is closer to 3/29/1642 than to 4/4/1642.We know that from 3/28/1642 to 3/29/1642, we have five days and one day.

Step 25: The values of the days can be found in this table.

Saturday, Sunday, Monday, Tuesday, Wednesday, and Thursday are the days.

Step 26: The numbers 1, 8, 15, 22, and 29 are the same in mod 7.

Step 27: The values of the months are in this table.

May 6 1 4 Jul 6 2 5 Oct Nov 0 3 5

Step 28: If it doesn't make sense now, use this table to know the values of the years.