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Any math wizards in here?

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    magnificentmagnificent Posts: 2,976
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    bart4858 wrote: »
    You can use a calculator to work it out semi-manually; add up the days in the intervening months:
    J  A  S  O  N  D  J  F
    31 31 30 31 30 31 31 28
    
    then add the days from 13th to end of June (17) and from start of March to 24th (24), giving 284 days.

    If you can work out the days to the start of each month in a year, that makes things easier, but you need to prepare a lookup table:
      J   F   M   A   M   J   J   A   S   O   N   D   (J)
      0  31  59  90 120 151 181 212 243 273 304 334 (365)
      0  31  60  91 121 152 182 213 244 274 305 335 (366) (Leap year)
    
    So for 13-June-2012, that is day # 152+13 or 165, and for 24-March-2013 it's day # 59+24 or 83. (Some diaries will give you this day number directly.) Now you're comparing years and days:
     2013  83
     2012 165
    
    To do the calculation, however, you need to normalise the day numbers, that is, make them refer to the start of the same year. With this example, convert the 83 to the number of days from the start of 2012, by adding the number of days in 2012 (366 as it was a leap year), which makes it 83+366 or 449. The calculation is now 449-165 or 284 days.

    Thanks. I'm looking at this as it's sort of making sense to my non math brain!

    I may well be over thinking since the manual way is the simplest albeit longer way, however, I like the idea of having the security of the calculator to confirm; plus it will save me valuable time under exam pressure ;-)
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    John259John259 Posts: 28,470
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    IqoniqIqoniq Posts: 6,299
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    My calendar on my phone gives me the number of the day on it, and the week too. Easier than having to faff around with a calculator.
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    gomezzgomezz Posts: 44,625
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    Once upon a time I might have been able to program my TI57 calculator to do it. These days a better solution is to use an app on your phone such as

    https://play.google.com/store/apps/details?id=com.kentbroadbent.nowandthen&hl=en
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    magnificentmagnificent Posts: 2,976
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    John259 wrote: »

    No I haven't - but I have now! thanks

    Goes to show it's not such an unusual question.
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    magnificentmagnificent Posts: 2,976
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    Iqoniq wrote: »
    My calendar on my phone gives me the number of the day on it, and the week too. Easier than having to faff around with a calculator.

    Exactly, but we're not allowed to take our phones in with us.
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    magnificentmagnificent Posts: 2,976
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    gomezz wrote: »
    Once upon a time I might have been able to program my TI57 calculator to do it. These days a better solution is to use an app on your phone such as

    https://play.google.com/store/apps/details?id=com.kentbroadbent.nowandthen&hl=en

    No phones allowed :)
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    codebluecodeblue Posts: 14,072
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    This is pretty simple to do in excel, when things are converted to serial dates.

    Because calendars are, we'll, completely illogical and based on nothing, time and date calculations are ridiculous without excel.
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    codebluecodeblue Posts: 14,072
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    Is there a way to work out on a calculator how many days there are between:

    13 June 2012 and 24 March 2013 inclusive?

    Subtract one from the other in excel.
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    gomezzgomezz Posts: 44,625
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    No phones allowed :)
    Why not. A phone is, amongst many other things, a calculator.
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    magnificentmagnificent Posts: 2,976
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    gomezz wrote: »
    Why not. A phone is, amongst many other things, a calculator.

    It runs the risk of people cheating - which is understandable.
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    gomezzgomezz Posts: 44,625
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    Cheating? I thought you wanted a practical solution for you to use. But if you are just asking out of idle curiosity and keep moving the goalposts, bye.
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    PrincessTTPrincessTT Posts: 4,300
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    Exactly, but we're not allowed to take our phones in with us.

    You need to know for an exam you're going to sit?
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    bart4858bart4858 Posts: 11,436
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    No I haven't - but I have now! thanks

    Take some care with that formula: (1) the month has to be 3 to 14, not 1 to 12 (convert as explained in the article); (2) these are integer divisions, which many calculators won't have ('floor' or 'round down' applied to each term might work if available).

    Otherwise it's quite fiddly if you have to write down the intermediate values (and the numbers get big). (Also, whatever method you use, it might not work for dates either side of 1752.)
    Goes to show it's not such an unusual question.
    No, there's nothing unusual about it. Other than trying to work it out manually..
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    magnificentmagnificent Posts: 2,976
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    PrincessTT wrote: »
    You need to know for an exam you're going to sit?

    Yes that's right. I need to know the calculation; the dates given in my op was merely illustrative. We are allowed a hard copy calendar and calculators - no phones - some crank might want to *ahem* phone a friend.
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    MaxatoriaMaxatoria Posts: 17,980
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    if you have a printed calendar surely you just count the number of full weeks and multiply by 7 and then add the odd days at the start/end on and is probably quicker and you'll probably have to memorise that formula as they may not allow you to bring in formula sheets etc
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    bart4858bart4858 Posts: 11,436
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    Yes that's right. I need to know the calculation; the dates given in my op was merely illustrative. We are allowed a hard copy calendar and calculators - no phones - some crank might want to *ahem* phone a friend.

    Any restrictions on what sort of calendar you can bring? Can you create your own? How many years should it cover (you mentioned 2012 and 2013 in your example)?

    If you can print your own, or even annotate an existing one, then just put day numbers against each date. For simplicity, these should be day numbers from the start of the same epoch, say from 1st January 2012 if that is the earliest date (so today would be day # 764).

    Then you just subtract the respective day numbers against the two dates! (If you get a negative number, it means you subracted in the wrong order; just ignore the sign.)

    (Less obvious - and less time-consuming to write out - would be day numbers for the start of each month; or rather, for the day before. Then you can just add the date on to it. Example, Jan-2012 would be 0, Feb-2012 is 31, and Feb-2014 is 762; then today is +2 so #764)
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    valkayvalkay Posts: 15,726
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    ...there's always one :p

    I will deploy my stock answer which is: the abbreviation maths is preferred in the UK and the abbreviation math is preferred in the USA; both are equally correct. #etymology

    But not in the U.K.>:(
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    lemoncurdlemoncurd Posts: 57,778
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    It's going to be embarrassing if a question about dates doesn't come up in this exam!
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    Jesse PinkmanJesse Pinkman Posts: 5,794
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    "Or 9 months, 11 days excluding the end date"

    So basically, you are 11 days overdue!

    See a doctor now!

    :D
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    jsmith99jsmith99 Posts: 20,382
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    Yes that's right. I need to know the calculation; the dates given in my op was merely illustrative. We are allowed a hard copy calendar and calculators - no phones - some crank might want to *ahem* phone a friend.

    So basically it's a mental arithmetic problem - one which I perform quite often to work out how long till my next holiday.

    Having arrived at the number of days, divide by 7 and look at the remainder. That should equal the number of weekdays between your first day and your last.
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