All Questions
Tagged with calendar-computations elementary-number-theory
11
questions
3
votes
2
answers
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Reliable Formula for repetition of of calendar
I am trying to get a formula for repetition of calendars (for years to repeat with same day-date pattern)
I could see the following rule in some of the online sites
a) If given year is at 1st ...
- 4,243
2
votes
2
answers
216
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Identical calendars
We can see, for example, that the years 2009 and 2015 have identical calendars. Similarly, 2000 and 2028.
I read once that given any year X at most 28 years later there will be another year Y, with ...
- 4,260
0
votes
0
answers
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
1
answer
348
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A leap year X has exactly the same calendar as another leap year Y. What can be the absolute difference between the values of X and Y?
A leap year X has exactly the same calendar as another leap year Y. What can be the absolute difference between the values of X and Y?
12
28
40
All of these
How can we find which leap year will have ...
- 149
12
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4
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Smallest future date which involves no repetition of a digit in the format DD/MM/YYYY [closed]
What is the smallest future date which involves no repetition of a digit in the format DD/MM/YYYY for the year? What is your approach?
- 309
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4
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Why isn't 1900 a leap year? [closed]
I searched leap years online and found that 1900 is not, contrary to what I thought, a leap year. But, why is it not if 1900 is divisible by 4:
$\frac{1900}{4} = 475$
My brother was working on his ...
- 787
2
votes
2
answers
116
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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
4
votes
6
answers
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Prove that in each year, the 13th day of some month occurs on a Friday [duplicate]
Prove that in each year, the 13th day of some month occurs on a Friday.
No clue... please help!
- 597
0
votes
2
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889
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Modular Arithmetic Calendars
If a calendar has 427 days in the year and 8 days a week and the first day of their current year, which is 1027 falls on the second day of their week. What day of the week will the first day of the ...
- 97
36
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6
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Prove that every year has at least one Friday the 13th
Everyone knows Friday the 13th is regarded as a day of bad luck.
Why does every year have at least one of this bad day?
Source: 2010 ISI B Math UGB
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