All Questions
Tagged with calendar-computations modular-arithmetic
20
questions
0
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Dates on which a day falls, in given month and year.
I was recently given the following problem on a test:
Find the dates on which Sunday fell in July, $1776$.
First, I noted the date on the day of test — $15$ October $2023$ to be a Sunday. Thereafter,...
- 3,321
0
votes
1
answer
40
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A formula to determine the number in a given sequence
I'm working with some specific numbers concerning a calendar calculation.
Basically, 13 years in a sequence correspond to 13 different numbers:
Year
Given number
Year 1
1
Year 2
10
Year 3
6
Year ...
- 276
1
vote
0
answers
235
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Finding Anchor day of any year using Doomsday rule.
There is a formula or a method given by Sir John Conway to find any given year anchor day after year 1800 assuming that we are using Gregorian calendar .For example for finding anchor day (also known ...
9
votes
1
answer
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Formula to find the day of any date in Gregorian calendar derivation.
My teacher taught an expression to find the day of any date in the Gregorian calendar.
Expression:
$$ \bbox[5px,border:2px solid red]
{
D\equiv {d+c_m+c_y+c+\left\lfloor\dfrac c4\right\rfloor \pmod7}
}...
- 1,563
4
votes
2
answers
341
views
Question concerning the solution of a certain calendar problem involving modular arithmetic.
A question I was given is the following:
A certain month on the calendar has 31 days, and it has an equal amount of Mondays and Wednesdays. How many different kind of days(Monday to Sunday) can be ...
- 2,821
1
vote
1
answer
800
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How to find the week day of (any) given date? [duplicate]
How to find the week day of any given date?
Say we need to know in which week-day was June $25,2019$?
- 5,450
0
votes
1
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131
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"New Year falls more often on Sundays than on Mondays"
This is a question from a hungarian math contest from the year 1948.
It was Saturday on the 23rd October, 1948. Can one conclude that New Year falls more often on Sundays than on Mondays?
Well, I ...
- 4,794
0
votes
1
answer
142
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Tonalpohualli calculations
I was doing some math on the Tonalpohualli, the mexica ritual calendar. This calendar has 260 days divided in 13-days periods associated with 20 distinct symbols. Every 13-days period is called a ...
- 276
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0
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467
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Calculating which day of the week a date falls on using Gauss's algorithm and modulo arithmetic
I've been told there's a straightforward way to determine which day of the week a date falls on, by first using Gauss's algorithm, to find the day of the week of 1st of January. Then this can be ...
- 890
0
votes
2
answers
321
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Number of Tuesdays in five consecutive calendar years taken together is exactly 260. Which day of the week was 1st Jan. of the first of five years?
Number of Tuesdays in five consecutive calendar years taken together is exactly 260. Which day of the week was 1st January of the first of these five years?
I don't know at all how to do this ...
- 571
1
vote
2
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10k
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Monday falls on 20th March, 1995. What was the day on 3rd November, 1994?
Monday falls on 20th March, 1995. What was the day on 3rd November, 1994?
Days in November 1994( starting from 3rd)= $27$
Days in December 1994=$31$
Days in January 1995=$31$
Days in February 1995= $...
- 137
2
votes
2
answers
116
views
Friday the 13th future possible
A year normally has at most three Fridays the 13th. Year 2015 has three such days. What is the next year that has three Fridays the 13th again for the first time?
- 259
2
votes
4
answers
14k
views
Which day of the week will be $100$ days from now
If today is Wednesday, what day of the week will it be $100$ days from now?
Going forward $1,8,15,\dots,92,99$ days all result in Wednesday. So the $100$th day will be Thursday. But the solution ...
- 153
30
votes
3
answers
12k
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Decoding Gauss' Easter Algorithm
In 1800, Gauss published this algorithm for computing the date of Easter in a given year $year$:
$a = year \mod 19$
$b = year \mod 4$
$c = year \mod 7$
$k = \lfloor year/100 \rfloor$
$p =...
user139000
-2
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2
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How to find the day of the week for a given date?
Please help me with my math problem
How to find the day of the week for a given date?
Give some simple solution or short cut for this problem
Thanks in advance
