![]() ![]() Each decade is also assigned an offset number. Note that the first and last groups only differ in the final spot, and that the second and third groups are also similar, only differing by 1 in the second and third spots.ĭecade offset. One helpful approach is to split the twelve numbers into four groups of three: 622, 503, 514 and 624. You must memorise this table, but it is not as hard as it may seem. Each of the twelve months is assigned a number, as given in the following table: Jan For example, 0, 7, and 14 all leave a remainder of 0, 33 leaves a remainder 5, and 52 leaves a remainder of 3. The possible remainders are from 0 up to 6. You will have to practise finding the remainder of numbers (from 0 to 54) when divided by 7. Pressing the button will open a separate page for practising the calculations. This page generates random numbers and dates for you to test yourself, with the answers within easy (but not too easy) reach. In order to help you master them, we have prepared a separate practice web page. The four main parts of the calculation are described below. (It used to be you had to memorise times tables: now it's Time tables!) Also, you will have to memorise the green and purple tables below. Then, the key to becoming super quick at the date trick is to become really good at finding remainders after dividing by 7. We'll assume that you're already a pro at adding on single-digit numbers. This means that you can begin to calculate while the date is still being read out to you. Each calculation requires only one of the day, month or year components of the given date. ![]() The most difficult calculations are to add on single-digit numbers, and to find the remainder after dividing by 7.The amount of memorisation and calculation required is kept to a minimum.So, our recipe works very well for an audience of real people, but not so well if you are confronted by, say, the ghost of Marie Here, we have attempted to simplify the procedure as much as possible for dates in the most commonly requested range. Many people have written about this calendar trick, and there are as many approaches. The key is to streamline the calculations as much as possible. All we need is the day for a convenient reference date, together with the basic facts about our Gregorian calendar: the lengths of the months and the rules for leap years. Doing it quickly: four easy piecesĪs our example illustrates, it is fundamentally straightforward to calculate the day of the week of any date. It is very unlikely that you could perform these calculations quickly enough to impress anyone. Thursday again 425 weeks later, and 3 days after that will be a Sunday. Dividing by 7, we get 425 weeks with 3 days left over. Summing up, there are a total of (6 x 365) + (2 x 366) + (31 + 30) − 5 = 2978 days between the two dates. The difference between the two dates is six ordinary years, two leap years, one 31-day month and one 30-day month, and then go backwards five days (from the 25th of the month to the 20th). (If it doesn't work, check that JavaScript is enabled in your web browser.) ![]() Enter the date of your birth and push the button. ![]()
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