Here is how to calculate which day of the week that was (Lancaster, 2005): ... Find the Day of the week. ), with the exception that years divisible by 100 are not leap years…. u/bprogramming. This calculator will instantly tell you whether the date you entered is a Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday. Unlike 2/28 or 2/29, 3/0 is always the last day of February, regardless of whether or not it is a leap year. The “Quad-year” of any given year is the greatest number that is both less than or equal to the given year and divisible by 4. These Year-days are called “Big Tuesdays” (just to help you remember them). You'll quickly see the result in the Day of the Year box, which will show the day of the week as well as the day number of the year. Leap year: 3/-42 ≡ 2/-13 ≡ 1/18; normal year: 3/-42 ≡ 2/-14 ≡ 1/17. There is a useful mnemonic to distinguish between months with 31 days and fewer than 31 days. In 2015, this special day of the week, which Conway calls "Doomsday," was a Saturday. 1600 or 1200), adding 100 years subtracts 2 from the day of the week. That’s fine though because you already know that the Century-day of every Big Tuesday-century is TWO’Sday. This only works when the larger of the two adjacent centuries is not a Big Tuesday-century. To change your work hours In the Start time and End time lists, click the start time and end time of your work day. So to calculate what the day of the week is going to be 237 days from this Monday, you first need to calculate 237 mod 7. Zeller's Algorithm can be used to determine the day of the week for any date in the past, present or future, for any dates between 1582 and 4902. We may also think of months as having days greater than 31. For example, in ANY year, 3/0 and 3/-14 are both Doomsdays, but in a leap year February has 29 days, so 3/-14 ≡ 2/15, while in a normal year February has 28 days, so 3/-14 ≡ 2/14. In our example, 1640-4*1 ≡ 1636, 1*-2 ≡ -2, and 5+(-2) ≡ 3, so the Quad-day of 1642 is Wednesday (as mentioned previously). For instance, it seems that 20 percent of the people know the day of the week they were born on, so there will often be someone around to check out if you are correct. We know 4/4/1642 is a Doomsday, so we add 14 days to discover that 4/18/1642 is a Doomsday. Don't give up, though. A leap year has two Sunday letters — one for before, and one for after, February 29. How to Perform Calendar Calculations in Your Head. Your salaried staff members work 40x15, a total of 600 hours a week. You have to be careful when going from March to January as well. Watch out for leap years. 659k members in the LearnUselessTalents community. Tuesday + 1 = Wednesday. "This page will teach you a simple algorithm to calculate mentally the day of the week corresponding to any given date. We can add 84 years without affecting the day of the week to get that -7216 is a THREE’Sday. But what they can do is perhaps one more thing than you can do.". These should be easy to remember because it is 7,14,21,28, and we're doing math by 7s because there are 7 days per week. Since the Year-day of 1224 is Thursday, the Dozen-day of 1234 is also Thursday. The “Century-year” is the first year of any given century. Estimated Foetal Weight Calculator. 2. This formula could even 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 one’s head and then perform the calculation quickly and precisely, which are the goals of the process explained here. For 2006, it is A. The method is based on one developed by John Horton Conway, and is described in Winning Ways, a book that he wrote with Berlekamp and Guy. We know that 7 x 17 is 119, leaving a remainder of 6: To calculate day-of-week for years farther away (say 1970 or 1900 or 1800) it might help to memorize key years and the base day of that year, rather than counting from 2007 / Wednesday back to 1800 (don't forget leap years). Calculating the Day of the Week in Your Head, a fun little exercise in calculating the day of the week - in your head. If you want to find the day of the week for a modern date (like your birthday), use the second section! The four-number cycle (0-5-3-1) of the Century Table repeats itself indefinitely, as shown in the table by the 0 for century 2000. Conveniently, the last day of February (the 28th in a regular year or the 29th if it's a leap year) also falls on this day. I’d like to read a csv file into a pandas dataframe, parse a column of dates from string format to a date object, and then generate a new column that indicates the day of the week. If you are not in a Big Tuesday-century, then you can find the Century-day as follows. For example, 1 ≠ 8, but 1 ≡ 8 (mod 7). Next, we must find Dozen-year. If you practice enough, you will eventually memorize more Doomsdays and all of the common Century-days (like the 1900s ≡ 3 and 2000s ≡ 2). More examples of how modulo behave are -15 ≡ -1 ≡ 6 (mod 7) and 4 ≡ -3 ≡ 7004 (mod 7). Watch out for people who may give you dates that do not exist just to trick you, e.g., April 31st (there aren't 31 days in April) or February 29, 1900 (this turn of the century year is not a leap year). Calculating the Day of the Week in Your Head As today is ‘Friday the 13 th’ we thought we’d introduce a fun little exercise in calculating the day of the week - in your head . You don’t have to just add or subtract 7 at a time though; you can use any multiple of 7. Taste buds form on your baby's tongue. (Important note: this does not mean that April 4, 2001, was also Tuesday. Also, memorize 7/11, 11/7, 9/5 and 5/9 (Memory aid: The people at the 7/11 work from 9 to 5, and reverse the numbers too). Conway's method uses the fact that the following dates always fall on the same day of the week in any given year. To get to the Year-day of a year immediately preceding a normal year, subtract one from Year-day of the (larger) normal year. Throughout the guide you will see (and have been seeing) congruence symbols, ≡, rather than equals signs, =, because 71 does NOT equal 8, but they are equivalent to determine the day of the week. Create a day-of-week column in a Pandas dataframe using Python. The basis of nearly all the algorithms to calculate the day of the week is: 1. This weekday calculator can find the day of the week of any date. Your 10 part-time employees work 20x10, a total of 200 hours a week. 1600-1699 or 1200-1599, but not 1400-1799), beginning from any Big Tuesday-year (i.e. If you’re given a date like 4/20/1642, which is not a Doomsday, then simply find the nearest Doomsday by repeatedly adding or subtracting 7 to known Doomsdays. The Century Code for dates in the 2000s is 6. The swap rate is credited or debited once for each day of the week when a position is rolled over, with the exception of Wednesday, when it is credited or debited 3 times (i.e. For March through December, the Sunday Letter is E. For 2009, the Sunday Letter is D. (Again, one step back. April, June, September, and November have 30 days. The years, taken at ten-year intervals, fall into a pattern. Subtract 4 from the Quad-year, 1640, until you get to the Dozen-year. Years that are divisible by 400 are called “Big Tuesday-years,” and centuries that have Century-days that are also Big Tuesdays are called “Big Tuesday-centuries.” Thus, the Year-day of 1600 is a Big Tuesday. From Jan 1 to June 30 of this year (2012), for instance, is 182 days (assuming both endpoints are included). Once you've calculated those four values, simply add them up and calculate the remainder of a division by seven (so that's modulo 7) and look up the day of the week in the following table: Week 24. Note that the Dozen-days for 1235, 1226, and 1229 are all Thursdays as well; while the Dozen-days for 1236 and 1238 are not the same (they are, in fact, Fridays). Here’s a graphic for the Doomsday numbers. Build up your speed over time. Russia only adopted it after the Russian Revolution. The “Dozen-day” of any given year is the Year-day of the Dozen-year. Doomsday Calculator – Calculate the weekday of any date in your Head; Week Number Calculator – Find the week number for any date; Date Calculator – Add or subtract days, months, years; Add to or subtract from a date and time; Duration Between Two Dates – Calculates number of days. are -1400, NOT -1300 because -1400 comes before -1300. You now have 1 day-of-week for every month. To convert 8/-6 into a normal date, simply add the number of days in the 7th month (July). From this, you should be able to easily calculate the day-of-week for any date in 2007. Use this simple birthday calculator to find the day of the week of birth based on a birthdate. The Doomsday Algorithm was developed for many years by John Horton Conway. So you should always ask the question 'What Country'?' Under Work time, do one or more of the following:. Thus, February 15th is a Doomsday during leap years, but February 14th is a Doomsday during normal years. Select a blank cell which you will place the day of week at, and type one of the below formulas into it, then press Enter key to get the weekday. Use the month's Doomsday to find the day you need. They are easy to memorize, and once one has this down pat, some simple calculations allow you to do this for any year. Simply type your date of birth in the box below, and it will tell you ... honest! For example, the Dozen-year of 1234 is 1224, because of 1224-1200 ≡ 24 ≡ 12*2, and no larger years that are still less than or equal to 1234 yield a positive difference with 1200 that is divisible by 12. Remember that you can add or subtract any multiple of 7 to a Number-day. Find how many 4's go into the remainder evenly. No this is not a typo; 3/0 is simply another way of thinking about the last day of February. When using this method, the due date is calculated by adding 280 days (or 9 months, the common length of a pregnancy) to the first day of your last menstrual period. These are easy to remember for Americans or Europeans because of the symmetry. We first need to find the Century-day of the -1700s. 1 divided by 7 is 0, with no remainder. Wednesday is thus also the Year-day of 1640. Other explanations of the Doomsday Algorithm and why it works can be found at the following URLs: http://en.wikipedia.org/wiki/Doomsday_rule#Julian_calendar, http://en.wikipedia.org/wiki/Astronomical_year_numbering, http://www.ted.com/index.php/talks/arthur_benjamin_does_mathemagic.html, http://en.wikipedia.org/wiki/Doomsday_rule#Overview_of_all_Doomsdays, https://cs.uwaterloo.ca/~alopez-o/math-faq/node73.html, https://www.scientificamerican.com/article/calendar-algorithm/, https://www.timeanddate.com/date/doomsday-weekday.html, https://cosmosmagazine.com/mathematics/magic-or-maths-find-the-day-of-the-week-for-any-date, http://thescienceexplorer.com/technology/how-calculate-day-week-any-date-until-2099, https://web.williams.edu/Mathematics/sjmiller/public_html/hudson/Ekness____Doomsday%20Presentation.pdf, http://quasar.as.utexas.edu/BillInfo/doomsday.html, Please consider supporting our work with a contribution to wikiHow. So it might be a good idea to prepare in advance some quick comeback like, "You know, you're right, they can. The following calculator helps you to address these variations. That's exactly 26 weeks, so there are exactly 26 of each day of the week. Success will gradually come. with the exception that years divisible by 400 are leap years. Approach: The Day of the Week For Any Date feat combines both memory and mental math. Once again, remember to watch out for leap years, like 18,400. Subtract 100 from the Century-year until you get to a Big Tuesday-year. 3+2 ≡ 5, so the Dozen-day of 1642 is Friday. With time,… Pig Weight Calculator Enter Length Enter Girth Select Unit of Measurement InchesCentimetres As the day of reckoning approaches for the two pigs, it’s time to see how well they’ve been growing. Footprints and fingerprints have formed. If the date were 6/20/1642, then you would subtract 7 days twice to discover that 6/20/1642 is the same day of the week as 6/6/1642, which is a known Doomsday. The “Century-day” of any given century is the “Year-day” of the first year of the century. Close • Posted by. In this tutorial, you will find a variety of useful formulas to add and subtract dates in Excel, such as subtracting two dates, adding days, weeks, months and years to a date, and more.. Whether you're wondering what day of the week your parents got married or want to check the weekday that a significant historical event like the terrorist attacks on the USA on September 11th 2001 happened, our Day of the week calculator will be able to work it out in a jiffy. Besides the formula, all you need to memorize is a single Doomsday date for each month and your year's anchor date. does not affect) the day of the week. Last Updated: July 2, 2020 To create this article, 68 people, some anonymous, worked to edit and improve it over time. Century Table and Year Value. The formula is Month Code + Day + Year Code and then use multiples of seven to get as close as you can to the answer and then the remainder is the Day Code that gives the Day. In order to calculate how much your employees cost you, you're going to first want to find the gross hourly rate. We can all calculate the day of any week mentally just like the character played by Dustin Hoffman in the movie “Rainman”. 1700-1799 but not 1704-1803), beginning from any Quad-year (i.e. If you do this successfully, you will always have the optimum number of staff in your contact centre and they will be blocked around the call-arrival pattern, like in the graph below. The pattern looks like this: 1600 ≡ TWO’Sday ≡ 2, 1700 ≡ Sunday ≡ 0, 1800 ≡ FIVEday ≡ 5 ≡ -2, 1900 ≡ THREE’Sday ≡ 3 ≡ -4, 2000 ≡ TWO’Sday ≡ 2 ≡ -5, and so on. 4. Next, tap the knuckle of your middle finger and say “March.” Notice as you continue that all of the months with 31 days are on knuckles, while all of the months with fewer days are in gaps. So the value for the 3300s would be 5. Which one is correct? In numerical calculation, the days of the week are represented as weekday numbers. Prev Another quick way to increase your speed is to memorize some January and February Doomsdays for non-leap years, like 1/10 and 2/0. For example, the Century-day of the 1800s is Friday, because you subtract 100 twice to get 1600, which is a Big Tuesday-year (because it’s divisible by 400). Example solve 2 I will now detail the process I use in how to work out the answers in my head with a few shortcuts. April 4, 2001, was a Wednesday.) This article has been viewed 380,269 times. The Century-year, -7300, is one century before a Big Tuesday-century, so the Century-day is THREE’Sday. Calculate the day of the week for any date in your head… {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/0\/01\/Calculate-the-Day-of-the-Week-Step-1.jpg\/v4-460px-Calculate-the-Day-of-the-Week-Step-1.jpg","bigUrl":"\/images\/thumb\/0\/01\/Calculate-the-Day-of-the-Week-Step-1.jpg\/aid47853-v4-728px-Calculate-the-Day-of-the-Week-Step-1.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"