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I am posting after a long time here. I am having trouble finding solution to this types of problem. Please help me out on this case:

If the 1st December, 1994, was Thursday, then what was the day on the same date in year 1995?

All I know it's related to Doomsday rule from Dr. John Conwa, but I need a clear explanation on how the calculation actually works.

Please help me out here.

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  • $\begingroup$ $1995$ was not a leap day so $365 \equiv 1 \pmod 7$. So it should a Friday. $\endgroup$ – Mohammad Zuhair Khan Apr 22 at 15:52
  • $\begingroup$ The question in the title differs from the one in the body. If you're curious here's about the title one: math.stackexchange.com/q/16945/515527 $\endgroup$ – Zacky Apr 22 at 16:04
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$1994$ and $1995$ aren't leap years, thus both of them have $365$ days.

The same day repeats exactly after $7$ days (that's what week is) so basically after $700$ days ($700=7\cdot 100$) it's still a Thursday.

Now we are $365$ days away and $364$ is the last multiple of $7$ up to $365$ thus after $364$ days it's still Thursday and obviously after a day it would be Friday.


If it were to be let's say $20$ February $2000$ a Monday (in a leap year), by the same logic $20$ February $2001$ would be Wednesday.

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    $\begingroup$ Thank you very much. The rule is cleared to me now. $\endgroup$ – Md. Imran Hossain Apr 23 at 4:55
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Hint:

Taking Dec 1, 1994 (Thursday) as Day-1. What is the date on Day-365 and hence the date on Day-366? What is the day on Day-8? On Day-15? On Day-22?

Can you take it from here?

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