another application of maths

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   Very interesting post, Naba.

What you say involving dates is essentially correct, but there is a little known flaw in your logic.  Normally, years which are divisible by four are leap years with 366 days (e.g., 1996, 2000, and 2004 were all leap years).  

HOWEVER, years which end in 00 are only leap years IF they are divisible by both 4 AND 400.  So, while the years 1600 and 2000 are leap years, the years 1700, 1800, and 1900 were NOT leap years.

Because of this complication, the years 1452 and 2012 end up having different calendars, and April 15, 1452 turns out to have been a Thursday and not a Sunday.

I think your claim about the 28 year cycle is correct, UNLESS the time period in question crosses one of the weird years such as 1900, which throws off the calculation.

http://en.wikipedia.org/wiki/Solar_cycle_(calendar)

*************************

If I may go down "memory lane" for a moment: I became aware of this weird leap year rule way back in 1981 when I started my first full time job as a computer programmer.  I was examining a subroutine written by a former employee which calculated the number of days between two dates, and I saw a section of code which only made sense if (for example) the years 1900 and 2100 were NOT leap years.

Although I've got to give that programmer full marks for completeness, I don't think I'd give him a high mark in practicality.  After all, there is no possibility of that section of code being executed for another 86 or so years.  I'm sure by now that old computer is destroyed and the computer program is no longer in existence.

On the other hand, I as a Christian and you as a Muslim no doubt both believe that we should "do our best in all things."  So, in a sense, that programmer was being a good Muslim (or a good Christian, depending upon his religion) by being so complete in his programming.

Alas, the programmer ignored the likelihood that the year 4000 will NOT be a leap year (because our calendar will, by then, require an additional one day correction).  Still, a program written in the year 1981 which is guaranteed to function correctly for 2019 years is a significant accomplishment. 

Edited by Reepicheep - 08 February 2014 at 6:32am

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Reepicheep Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 06 November 2006 Status: Offline Points: 324	Post Options Post Reply Quote Reepicheep Report Post Thanks(0) Quote Reply Posted: 08 February 2014 at 6:14am
	Very interesting post, Naba. What you say involving dates is essentially correct, but there is a little known flaw in your logic. Normally, years which are divisible by four are leap years with 366 days (e.g., 1996, 2000, and 2004 were all leap years). HOWEVER, years which end in 00 are only leap years IF they are divisible by both 4 AND 400. So, while the years 1600 and 2000 are leap years, the years 1700, 1800, and 1900 were NOT leap years. Because of this complication, the years 1452 and 2012 end up having different calendars, and April 15, 1452 turns out to have been a Thursday and not a Sunday. I think your claim about the 28 year cycle is correct, UNLESS the time period in question crosses one of the weird years such as 1900, which throws off the calculation. http://en.wikipedia.org/wiki/Solar_cycle_(calendar) ************************* If I may go down "memory lane" for a moment: I became aware of this weird leap year rule way back in 1981 when I started my first full time job as a computer programmer. I was examining a subroutine written by a former employee which calculated the number of days between two dates, and I saw a section of code which only made sense if (for example) the years 1900 and 2100 were NOT leap years. Although I've got to give that programmer full marks for completeness, I don't think I'd give him a high mark in practicality. After all, there is no possibility of that section of code being executed for another 86 or so years. I'm sure by now that old computer is destroyed and the computer program is no longer in existence. On the other hand, I as a Christian and you as a Muslim no doubt both believe that we should "do our best in all things." So, in a sense, that programmer was being a good Muslim (or a good Christian, depending upon his religion) by being so complete in his programming. Alas, the programmer ignored the likelihood that the year 4000 will NOT be a leap year (because our calendar will, by then, require an additional one day correction). Still, a program written in the year 1981 which is guaranteed to function correctly for 2019 years is a significant accomplishment. Edited by Reepicheep - 08 February 2014 at 6:32am

NABA Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Male Joined: 13 December 2012 Location: India Status: Offline Points: 867	Post Options Post Reply Quote NABA Report Post Thanks(0) Quote Reply Posted: 08 February 2014 at 2:34am
	Assalamalecum, all praise to Allah, the most forgiving and merciful, I will start with the verse ch 96 v 1-5-recite in the name of lord who created u from clay, recite, and ur lord is generous and he taught to u by pen and he taught the man that he didn't know.i always had liking of numbers I shud say Allah gave me the means to do, lets take an example da vinci was born on 15.4.1452.can we know what day was this????? But with the help of maths we can know what day this date was.in this case was sunday.how?? I explain it eg ur 1971 and yr 1999 will have same dates as it is, or u can say date with same days return every 28 yrs exactly bcoz 28 yrs-10227 day which is divisible by 7, so difference between 2012 and 1452 is 560 which is divisible by 28, therefore 15.4.12 was sunday so as to 1452, by this method we can determine any date whether past or future eg dates of yr t14 will b equal to 2126 bcoz difference is 112 which is divisible by 28 I.e 8.2.2126.