JP2000122998A - Method and device for calculating day of week - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the scale of a circuit by reducing the scale of operation for calculating a day of the week. SOLUTION: In the day-of-week calculation method, the A.D. year of a required date is divided by 400, an obtained remainder E, the number U of intercalary years of the year having the remainder E, an intercalary year addition day L to be '1' when the required date is an intercalary year or '0' when the required date is not an intercalary year, the number F of days from January 1 to the end of the preceding month of the required month, and a required day C are added, and a remainder obtained at the time of dividing the added value by '7' is used for a day-of-week conversion table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a day calculation method and a day calculation device for calculating a day corresponding to an arbitrary date in the Christian era (Gregorian calendar).

[0002]

2. Description of the Related Art Conventionally, a specific date (for example, A
When calculating the day of the week corresponding to the month B / C), a reference date (for example, January 1, 1900) and the day of the week (Sunday) are set in advance, and the date from the reference date to the date B / C of the year A is calculated. The number of days was calculated, and the day of the week was calculated by the remainder when dividing the number of days by 7.

[0003]

With the above-described conventional day-of-the-week calculation method, it is impossible to calculate a date before the reference date. could not. Also, when setting a reference date, it is necessary to set a day of the week of the reference day, and it is necessary to investigate when the day of the reference day is.

Further, in order to calculate a date from a reference date, it is necessary to multiply the number of years from the reference date to a desired year by 365, and there is a problem that the calculation result becomes large and the circuit scale becomes large. Was.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a day-of-week calculating method for calculating a desired day of the week on B / C of the year A. 4
Calculating a first remainder E by dividing by 00; calculating the number U of leap years up to the previous year of the A year (first remainder E years); and dividing the first remainder E by a binary number. When written, the lower two bits become 00, and the first remainder E
Is not 100, 200, or 300, the step of determining that the year A is a leap year, and when the year A is a leap year, the leap year addition date L is set when the month B is 3 or more. Setting the leap year addition day L to 0 when the B month is 2 or less; and setting a desired month B from January 1
Checking the number of days F until the last day of the previous month, the first remainder E, the number U of leap years, and the leap year addition date L
, The number of days F and the desired day C, and the sum M
And calculating a day of the week by applying a second remainder N obtained by dividing the sum M by 7 to a day of week calculation table.

[0006] Also, with respect to the desired date B / C / A,
A day calculating device for calculating the day, wherein A is 400
Means 1 for calculating the first remainder E by dividing by E, means 2 for calculating the number of leap years (first remainder E years) U up to the previous year of A, the first remainder E and the desired Means 3 for judging whether a desired year A, B, and C of the year B is a leap year from month B of the month B, and sets leap year addition day L to 1 if it is a leap year, and outputs leap year addition day L as 0 if it is not a leap year. Means 4 for outputting the number of days F from January 1 to the last day of the month preceding the desired month B, the first remainder E, the number U of leap years, the date L of leap years added, the number of days F, Means 5 for adding the day C, which is a desired day, to calculate the sum M, and applying the second remainder N obtained by dividing the sum M by 7 to the day of the week calculation table to determine the day of the week. The present invention provides a day-of-the-week calculation device including means for calculating.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The day of the week changes every seven days,
Dividing 365 days, which is the normal number of days in a year excluding leap years, by 7, gives 1 more than 52 days. This means that the day of the week is one year
It means moving forward day by day. Specifically, 19
That is, Thursday, January 1, 1998, and Friday, January 1, 1999. In the Gregorian calendar, the same day is the same day of the week in a 400-year cycle. That is, January 1, 2000 and January 1, 2400 are the same day of the week.

From these facts, if the remainder of the year is divided by 400, that is, if the day of the week is calculated from the year 0 to the year 399, it is possible to calculate the day of the week with a small numerical value to be handled.

Hereinafter, a day of the week calculation method and a day of the week calculation apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the day of the week calculating apparatus according to the present invention. FIG. 2 is a flowchart showing the operation of the day of the week calculation device according to the present invention. FIG. 3 is a diagram illustrating a month-day conversion table of the method of the day-of-week calculating device according to the present invention, and FIG. 4 is a diagram illustrating a day-of-week conversion table of the day-of-week calculating device according to the present invention.

According to FIG. 1, first, a desired date A, B, C is input manually or automatically. The input date is divided into year, month, and day, and the year A is input to the division unit 1. The division unit 1 calculates a first remainder E when the year A is divided by 400.

The leap year calculator 2 calculates the number U of leap years based on the first remainder E. However, since the year A is divided by 400, it is the number of leap years within the last 400 years.

On the other hand, the leap year determining section 3 determines whether or not the desired year A is a leap year. The rule for leap years is "1.400
The year divisible by is a leap year. 2. Years that are not divisible by 400 but divisible by 100 are not leap years. 3.10
Years that are not divisible by 0 and are divisible by 4 are leap years. However, in the present invention, the first remainder E which is the output of the division unit 1 is used. Since the range of the remainder E is 0 to 399, the first remainder E is 0. It is determined whether the desired year A is a leap year by examining whether it is or a multiple of 4, 100, 200, or 300. Further, when the desired year A is a leap year, it is determined whether the desired month B is 3 or more. If the desired month B is 3 or more, the leap year addition date L = 1. Set to 0. This is because when the desired month B is 3 or more, it is necessary to add one day for a leap year.

Next, the table conversion unit 4 determines the number of days F according to a desired month B by using a month-day number conversion table shown in FIG.

Then, the number U of leap years, the day L of addition of leap years, the number of days F, and the desired day C are added by the adding section 5, and this value M is divided by 7 by the dividing section 6 to obtain the second remainder N Ask for. According to the second remainder N, a desired day of the week is obtained from the day of the week conversion table shown in FIG.

Next, the operation of the embodiment of the day of the week calculating apparatus according to the present invention will be described with reference to FIG.

First, assuming that the desired date is B, C, A, the desired year A is divided by 400 to obtain a first remainder E (step S01).

Next, the first remainder E years to the desired year A (for example, if the desired year is 1998, the first remainder E
= 398 years). First, it is determined whether or not the first remainder E is 0 (step S02).
If the remainder is 0, the number U of leap years is also 0 (step S03), and if the first remainder E is not 0, the number U of leap years is as shown in equation 1 (step S04).

[0019]

(Equation 1) Further, it is determined whether or not the desired year A is a leap year. A leap year is a leap year if it is divisible by 1.400.
2. Years that are not divisible by 400 but divisible by 100 are not leap years. A year divisible by 4 is a leap year if it is not divisible by 3.100. In the present invention, the first remainder is 0 to 3
Since it is between 99 and 99, the first condition “year divisible by 400” can be excluded. Therefore, the determination of the leap year can be performed as follows (step S0).
5 to Step S08). First, when the first remainder E is represented by a binary number, it is checked whether or not the lower two bits are 0. This is because when the lower 2 bits are 0 in a binary number, this value is a multiple of 4 (step S05). However, when the first remainder is 0, it is not a multiple of 4 but may be a leap year.

On the other hand, when the first remainder E is represented by a binary number and the lower 2 bits are not 0, it is determined that the desired year A is not a leap year, and the process shifts to step S11. If the lower two bits of the first remainder E in binary are 0, it is determined that the desired year A may be a leap year, and the process proceeds to step S06.

In step S06, the first remainder E is 10
Check to see if it is zero. And the first remainder E is 10
When it is 0, the process proceeds to step S11. When the first remainder E is not 100, the process proceeds to step S07.

In step S07, the first remainder E is 20
Check to see if it is zero. And the first remainder E is 20
When it is 0, the process proceeds to step S11. When the first remainder E is not 200, the process proceeds to step S08.

In step S08, the first remainder E is 30
Check to see if it is zero. And the first remainder E is 30
When it is 0, the process proceeds to step S11, and when the first remainder E is not 300, the process proceeds to step S09.

By performing such processing, the desired year A
If is a leap year, the process proceeds to step S09, and if not, the process proceeds to step S11. As described above, according to the leap year determination method in steps S05 to S08 described above, since the comparator can be configured by four comparators without dividing the actual desired year A, the circuit scale is reduced.

Next, when the desired year A is a leap year, it is checked whether or not the desired day C is before February 29. For this purpose, it is determined whether or not the desired month B is 3 or more.
If so, the process proceeds to step S10, and if less than 2, the process proceeds to step S10. And
In step S10, the leap year addition day L = 1 is set, and in step S11, the leap year addition day L = 0 is set, and the process proceeds to step S12.

In step S12, the number of days F from January 1 to the end of the previous month of the desired month B is obtained using the month-day number conversion table shown in FIG. 3 (one day of a leap year is not counted).
Move to step S13.

In step 13, the numerical values obtained so far are summed and the numerical value is divided by seven. Specifically, the first
The remainder E, the number U of leap years, the added day L of leap years, the number of days F, and the desired day C are summed and divided by 7. And the obtained second
By using the day of the week conversion table shown in FIG.

Next, a description will be given using specific numerical values.

For example, when the desired date is December 31, 1998, A = 1998, B = 12, C = 31
It is.

The first remainder E when A is divided by 400
Is 398, and the number U of leap years is 97.

Then, whether or not 1998 is a leap year can be determined by expressing the first remainder E = 398 in binary notation as 11000.
1110, and its lower two bits become 10. Therefore, 1998 is not a leap year because the lower two bits when the first remainder E is represented by a binary number are not 00. Therefore, L = 0.

Further, the number of days from January 1 to the end of the previous month of the desired month B is obtained from the month-day number conversion table of FIG. Since month B = 12, F = 334.

Next, when the obtained numerical values are summed, the remainder N is calculated by dividing the first remainder E + the number of leap years U + the number of added days L + the number of days F + the desired date C = 398 + 97 + 0 + 334 + 31 = 860 by 7. . Then N = 6,
From this value, it can be seen that the desired date is Thursday using the day conversion table shown in FIG.

[0034]

As described above in detail, according to the day of the week calculating method and the day of the week calculating apparatus according to the present invention, the year is set to 0 to 39.
Since the day of the week calculation is performed instead of the numerical value of 9, the numerical value to be handled can be reduced and the circuit scale can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a day of the week calculation method and a day of the week calculation device according to the present invention.

FIG. 2 is a flowchart illustrating an operation of a day calculation method and a day calculation device according to the present invention.

FIG. 3 is a diagram showing a month-day number conversion table;

FIG. 4 is a diagram showing a day of the week conversion table.

[Explanation of symbols]

 1, 6 division unit 2 leap year calculation unit 3 leap year judgment unit 4 table conversion unit 5 addition unit

Claims (2)

[Claims] 1. A day of the week calculation method for calculating a desired day of the week of B / C of the year A, wherein the year A is divided by 400 to calculate a first remainder E; Number of leap years up to the previous year of A (first remaining E years) U
And calculating the first remainder E in a binary number, the lower 2 bits become 00, and the first remainder E becomes 100, 200,
Determining that the year A is a leap year when it is not any of 300; setting the leap year addition day L to 1 when the month B is 3 or more when the year A is a leap year; Setting the leap year addition day L to 0 when the month is 2 or less; calculating the number of days F from January 1 to the last day of the month before the desired month B; and the first remainder E; Adding the leap year number U, the leap year addition day L, the number of days F, and the desired day C to calculate a sum M thereof, and dividing the sum M by 7 Calculating the day of the week by applying the second remainder N to the day of the week calculation table. 2. A day-of-week calculating apparatus for calculating a desired day of the week of B / C of the year A, wherein A is divided by 400 to calculate a first remainder E. Number of leap years up to the previous year of the year (first remainder E years) U
A desired year A B from the first remainder E and the desired month B
Means for judging whether the month C is a leap year, outputting a leap year addition day L as 1 when the month C is a leap year, and outputting 0 as a leap year addition day L when the month C is not a leap year; Means for outputting the number of days F up to the last day of the previous month; adding the first remainder E, the number U of the leap years, the leap year addition day L, the number of days F, and the day C which is a desired day. A day calculation device comprising: means for calculating the sum M; and means for calculating the day of the week by applying the second remainder N obtained by dividing the sum M by 7 to the day of the week calculation table.