day of the week function

[Larryrl]

I would like to find a function where I can have it tell me what day of the week it is for the first of the current month. Am wanting to do a computer calendar with slots to write in appointments kind of like a yearly planner.

[bplus]

Have you tried a search for calendar, there's at least 4 to find:
Pete, SMcNeill, SierraKen, bplus

[SMcNeill]

FUNCTION GetDay (m, d, y) 'use 4 digit year
    'From Zeller's congruence: https://en.wikipedia.org/wiki/Zeller%27s_congruence
    mm = m: dd = d: yyyy = y
    IF mm < 3 THEN mm = mm + 12: yyyy = yyyy - 1
    century = yyyy MOD 100
    zerocentury = yyyy \ 100
    result = (dd + INT(13 * (mm + 1) / 5) + century + INT(century / 4) + INT(zerocentury / 4) + 5 * zerocentury) MOD 7
    IF result = 0 THEN
        GetDay = 7
    ELSE
        GetDay = result
    END IF
    'Function changed to return a numeric value instead of a string for this program
    '    SELECT CASE result
    '        CASE 7: GetDay$ = "Saturday"
    '        CASE 1: GetDay$ = "Sunday"
    '        CASE 2: GetDay$ = "Monday"
    '        CASE 3: GetDay$ = "Tuesday"
    '        CASE 4: GetDay$ = "Wednesday"
    '        CASE 5: GetDay$ = "Thursday"
    '        CASE 6: GetDay$ = "Friday"
    '    END SELECT
END FUNCTION

[Pete]

The one I posted a few years ago is here: https://www.qb64.org/forum/index.php?topic=855.msg100586#msg100586

It was designed as a popup. I used to toggle to it when I needed to input a date into a WP app.

I checked it. It still runs fine on V2.0. I really should update it to work with the QB64 mouse. Oh well, add that to my to-do list.

Pete

[George McGinn]

Here's one based on the doomsday rule that may refer to a hypothetical event according to which the end of human life is at the highest possibility. There are many algorithms written to calculate which day of a week in a year has the highest possibility of doomsday falling on that day.

This program expands upon and is a generalized version of the Dooms Day Code program, where the formula used in combination with the "Special Dates" can easily calculate the Day Of Week (DOW) from a date without any complicated algorithms (such as the one that uses the Julian Date from a specific point in time).

This method is also used as a math trick to calculate the day of week in your head.

See: https://en.wikipedia.org/wiki/Doomsday_rule

Code: QB64: [Select]

1. OPTION _EXPLICIT
2. _TITLE "Day Of Week"
3. ' *** Dooms Day Code Used For Calculating The Day of Week ***
4. ' *** Written by George McGinn
5. ' *** Code shared under Creative Commons License "Universal 1.0 Public Domain (CC0 1.0)"
6. ' *** https://creativecommons.org/publicdomain/zero/1.0/
7. '
8. ' *** Program will run on Linux, Windows and MAC Systems.
9. '
10. '____________________________________________________________________________________________________________________
11. '
12. ' Doomsday may refer to a hypothetical event according to which the end of human life is at the highest possibility.
13. ' There are many algorithms written to calculate which day of a week in a year has the highest possibility of
14. ' doomsday falling on that day.
15. '
16. ' This program expands upon and is a generalized version of the Dooms Day Code program, where the formula used in
17. ' combination with the "Special Dates" can easily calculate the Day Of Week (DOW) from a date without any complicated
18. ' algorithms (such as the one that uses the Julian Date from a specific point in time).
19. '
20. ' See: https://en.wikipedia.org/wiki/Doomsday_rule
21. '
22. ' SPECIAL DATES
23. ' These are dates that when the Dooms Day Code for the year in question is calculated, these dates all have the
24. ' same DOW.
25. '
26. ' The "Speical Dates" or "Refernce Dates" where the Doomsday DOW code is the same through the currenly selected
27. ' year are:
28. '   4/4, 6/6, 8/8, 10/10 and 12/12 --> These set of dates are referred to as "Doubles"
29. '   5/9, 7/11, 9/5 and 11/7        --> Reverse dates
30. '   3/14                           --> PI Day
31. '   2/28 or 2/29                   --> Non Leap-year (2/28) or Leap-year (2/29)
32. '   1/3 or 1/4                     --> Non Leap-year (1/3) or Leap-year (1/4)
33. '
34. ' All these days have the same DOW. For example, if it is 9/7/2015, the Doomsday code for 2015 is 06 or "Saturday."
35. ' This means that all the above dates fall on Saturday in 2015 (use the non Leap-year dates).
36. '
37. ' To use this to find out what day-of-week 9/7/2015 falls on, find the closest day from the reference dates, and
38. ' do a simple addition or subtraction. The date 9/7 is the closest date, and we know that 9/7 is a "Saturday" based
39. ' on the calculated Doomsday code. We only need to subtract 5 from 7, giving us 2, then subracting 2 from 6, giving
40. ' us 4. DOW(4) = Thurdsday. So 9/7/2015 falls on a Thursday.
41. '
42. ' If we want to calculate the DOW that Christmas falls on in 2015 (12/25/2015) the same proceedure is used.
43. ' The closest reference date is 12/12. Subtracting 12 from 25 gives us 13. 13 MOD 7 = 6. Since 6 is one day short
44. ' of a whole week, we only need to subtract one day from the Doomsday Code ((7-6)-1)=5. Christmas 2015 is on Friday.
45. '
46. ' This program uses this logic to calculate any DOW from any date from 1583 to well into the future. Any date before
47. ' the Gregorian Calendar was adopted in your country will give you inaccurate results.  Check the following link:
48. '     https://en.wikipedia.org/wiki/List_of_adoption_dates_of_the_Gregorian_calendar_per_country
49. '
50. '
51. ' PROGRAM NOTES
52. '
53. ' This program uses both the Dooms Day algorithm and incorporates the mental math trick to calculate the Day-of-Week
54. ' in your head. By using this method makes the code (and process of) more understandable and slightly faster than
55. ' using the complex algorithms using the Julian Date and doing all the divisions by 4, 100 and 400 for Leap Years.
56. '
57. ' Below is a description of what each FUNCTION/SUBROUTINE does in this program:
58. '
59. ' floor          - A C++ Library that does not round up numbers when converting FLOAT to INTEGER. (Thanks to
60. '                  both Fleppie and Spriggs for this)
61. '
62. ' dooms_day_code - Calculates the Doomsday Code for the century of the supplied date. This is needed as input into
63. '                  the calculation of the actual year's Dooms Date code.
64. '
65. ' dooms_date     - Takes the century "anchor" code from dooms_day_code and calculates the Dooms Day code for the
66. '                  actual year of the date.  This will be used to calculate the Day-of-Week for the date supplied.
67. '____________________________________________________________________________________________________________________
68.  
69. DECLARE LIBRARY
70.     FUNCTION floor## (BYVAL num AS _FLOAT)
71. END DECLARE
72.  
73. DIM SHARED dict_day$(7)
74. DIM SHARED year, dow_anchor AS INTEGER
75.  
76. '*** map to store days value of anchor day can be known
77. dict_day$(0) = "Sunday"
78. dict_day$(1) = "Monday"
79. dict_day$(2) = "Tuesday"
80. dict_day$(3) = "Wednesday"
81. dict_day$(4) = "Thursday"
82. dict_day$(5) = "Friday"
83. dict_day$(6) = "Saturday"
84.  
85.  
86. main:
87. '*** Enter Year for Dooms Day Code and Display results
88.     INPUT "Enter YEAR (CCYY): "; year
89.     IF year < 1582 OR year > 2199 THEN
90.         PRINT "*** ERROR: Date Invalid/Out Of Range"
91.         GOTO main
92.     END IF
93.  
94. '*** Get the Doomsday Code for the anchor
95.     dow_anchor = dooms_day_code(year)
96.  
97. '*** Get the Doomsday Code using the century anchor for the year's actual Doomsday code and display
98.     PRINT "Doomsday in the year "; year; " = "; dict_day$(dooms_day(year, dow_anchor))
99.     END
100.  
101. '
102. ' *** End of Main
103. '____________________________________________________________________________________________________________________
104.  
105.  
106. '*** FUNCTIONS AND SUBROUTINES
107. '
108.  
109. FUNCTION dooms_day (year, anchor AS INTEGER)
110.  
111. DIM yr$, cc_str$, yy_str$
112. DIM yy, cc AS INTEGER
113.  
114. '*** Split out the century from the year and create two variables
115.     yr$ = STR$(year)
116.     yr$ = _TRIM$(yr$)
117.     cc_str$ = LEFT$(yr$, 2)
118.     yy_str$ = RIGHT$(yr$, 2)
119.     yy = VAL(yy_str$)
120.     cc = VAL(cc_str$)
121.  
122. '*** Dooms day formula by1 John Conway
123.     dooms_day = (yy + floor(yy / 4) + anchor) MOD 7
124.    
125. END FUNCTION
126.  
127.  
128. FUNCTION dooms_day_code (year)
129.  
130.     DIM y, anchor, yy, cc AS INTEGER
131.     DIM yr$, cc_str$, yy_str$
132.  
133. '*** Split out the century from the year and create two variables
134.     yr$ = STR$(year)
135.     yr$ = _TRIM$(yr$)
136.     cc_str$ = LEFT$(yr$, 2)
137.     yy_str$ = RIGHT$(yr$, 2)
138.     yy = VAL(yy_str$)
139.     cc = VAL(cc_str$)
140.  
141. '*** Decide the anchor day
142.     SELECT CASE cc_str$
143.            CASE "17"
144.                 anchor = 0
145.            CASE "18"
146.                 anchor = 5
147.            CASE "19"
148.                 anchor = 3
149.            CASE "20"
150.                 anchor = 2
151.            CASE "21"
152.                 anchor = 0
153.            CASE "22"
154.                 anchor = 5
155.     END SELECT
156.  
157. '*** Dooms day formula by John Conway
158.     dooms_day_code = ((floor(y / 12) + y MOD 12 + floor(y MOD 12) / 4) MOD 7 + anchor) MOD 7
159.  
160. END FUNCTION
161. '
162. ' *** End of Program Source
163. '____________________________________________________________________________________________________________________

[Pete]

I made a Mayan Calendar app, but it got erased in 2012. :(

Hey where's Larryrl or his brother Darrelry or his other brother Darrelry, anyway?

Hey George, since "Dooms Day" falls on a Sunday in 2021, do you have another version that gives the time. I'm barbecuing this Sunday, and if necessary, I'll start the coals early.

Pete

[George McGinn]

Donkey Dust!

I was looking for something clever for you @Pete, but I reran my code when all you posted was that doomsday in 2021 was on a Sunday.

The code that does what is described below is missing. I lost code (how novel!) A while back I consolidated all my BASIC code is a master directory in my SourceCode folder, and it appears I overlaid this program.

It should have allowed you to input a full date, and the doomsday code is for use in quickly calculating the DOW based on "Special" dates, like this "Special" programmer who preformed a doomsday event on his source code (DOH!)

' To use this to find out what day-of-week 9/7/2015 falls on, find the closest day from the reference dates, and
' do a simple addition or subtraction. The date 9/7 is the closest date, and we know that 9/7 is a "Saturday" based
' on the calculated Doomsday code. We only need to subtract 5 from 7, giving us 2, then subracting 2 from 6, giving
' us 4. DOW(4) = Thurdsday. So 9/7/2015 falls on a Thursday.
'
' If we want to calculate the DOW that Christmas falls on in 2015 (12/25/2015) the same proceedure is used.
' The closest reference date is 12/12. Subtracting 12 from 25 gives us 13. 13 MOD 7 = 6. Since 6 is one day short
' of a whole week, we only need to subtract one day from the Doomsday Code ((7-6)-1)=5. Christmas 2015 is on Friday.

[Pete]

No worries. I'm currently working on a program to calculate when Hell will freeze over. People ask me all the time, "Pete, when is it going to be finished?" I'll tell you the same thing I tell all of the rest of them. It will be finished when Hell freezes over.

What's that dear? Time for my meds again! Already? Argh.

Pete