B4J Code Snippet B4X - cHolidays - Determine when a certain holiday is

William Lancee · Dec 31, 2019

I couldn't resist to add Easter.

B4X:

#Region WhenIs_EasterDay
Public    Sub    WhenIs_EasterDay(ForYear As Int) As THolidayIs

            Dim HolidayIs As THolidayIs
            HolidayIs.Initialize
            HolidayIs.IsValid    = True
                        
            'This Haskell function computes the date of Easter Sunday for a given year, as used by the United States Naval Observatory
            
            Dim C As Long
            Dim N As Long
            Dim K As Long
            Dim I As Long
            Dim J As Long
            Dim L As Long
            Dim M As Long
            Dim D As Long
            
            C = Floor(ForYear / 100)
            N = ForYear - 19 * Floor(ForYear / 19)
            K = Floor((C - 17) / 25)
            I = C - Floor(C / 4) - Floor((C - K) / 3) + 19 * N + 15
            I = I - 30 * Floor(I / 30)
            I = I - Floor(I / 28) * (1 - Floor(I / 28) * Floor(29 / (I + 1)) * Floor((21 - N) / 11))
            J = ForYear + Floor(ForYear / 4) + I + 2 - C + Floor(C / 4)
            J = J - 7 * Floor(J / 7)
            L = I - J
            M = 3 + Floor((L + 40) / 44)
            D = L + 28 - 31 * Floor(M / 4)

            Dim EasterThisYear As Long = DateTime.DateParse($"${NumberFormat2(M, 2, 0, 0, False)}/${NumberFormat2(D, 2, 0, 0, False)}/${NumberFormat2(ForYear, 4, 0, 0, False)}"$)

                    
            HolidayIs.Month        = DateTime.GetMonth(EasterThisYear)
            HolidayIs.Day        = DateTime.GetDayOfMonth(EasterThisYear)
            HolidayIs.Year        = DateTime.GetYear(EasterThisYear)
            HolidayIs.DayOfWeek    = DateTime.GetDayOfWeek(EasterThisYear)

            Log("         Easter Day Is " &NumberFormat2(HolidayIs.Month, 2, 0, 0, False) &"/" &NumberFormat2(HolidayIs.Day, 2, 0, 0, False) &"/" &NumberFormat2(HolidayIs.Year, 4, 0, 0, False) &"  -  " &DEFINE_DaysOfWeek(HolidayIs.DayOfWeek))
            
            Return HolidayIs
End Sub
#end region

Robert Valentino · Dec 31, 2019

Good idea. That one slipped by

LucaMs · Dec 31, 2019

https://www.b4x.com/android/forum/threads/giorni-dellanno-senza-feste.91714/post-581037
(Note: I don't remember it ?)

HAPPY NEW YEAR

William Lancee · Jan 1, 2020

Since this is a multicultural forum I will post to chit chat to request contributions from others. There must be hundreds/thousands of holidays.

derez · Jan 1, 2020

I have a working application to check if a date is a Hebrew/Israeli Holiday/Event. It uses the Dateconvert library https://www.b4x.com/android/forum/threads/dateconvert-library.16770/post-95800. They usually move based on the Day Of Week. If anyone is interested I'll publish it. The following is just the names of the Holidays:

B4X:

Hag_name(0) = "ראש השנה"
Hag_name(1) = "יום הכיפורים"
Hag_name(2) = "סוכות"
Hag_name(3) = "חול המועד סוכות"
Hag_name(4) = "סוכות שני הושענא רבא"
Hag_name(5) = "שמחת תורה"
Hag_name(6) = "חנוכה"
Hag_name(7) = "צום עשרה בטבת"
Hag_name(8) = "ראש השנה לאילנות"
Hag_name(9) = "תענית אסתר"
Hag_name(10) = "פורים"
Hag_name(11) = "שושן פורים"
Hag_name(12) = "פסח"
Hag_name(13) = "חול המועד פסח"
Hag_name(14) = "פסח שני"
Hag_name(15) = "יום הזכרון לשואה ולגבורה"
Hag_name(16) = ""
Hag_name(17) = "יום העצמאות"
Hag_name(18) = "יום הזכרון לחללי צה''ל"
Hag_name(19) = "ל''ג בעומר"
Hag_name(20) = "שבועות"
Hag_name(21) = "צום י''ז בתמוז"
Hag_name(22) = "תשעה באב"
Hag_name(23) = "חג האהבה"
Hag_name(24) = "צום גדליה"
Hag_name(25) = "יום הזכרון ליצחק רבין"
Hag_name(26) = "יום ירושלים"

rabbitBUSH · Jan 1, 2020

William Lancee said:
I couldn't resist to add Easter.

Does this take care of Easter following a lunar cycle (not sure but I think it does)

And

Leap year:

C = (c/4)

If I recall from ComSci

exercises every 400th year is NOT a leap year... Not sure if your code accommodates for that.?

William Lancee · Jan 1, 2020

@LucasMs

You know, NOW I remember seeing your post. The algorithm is the same.

A thorough scholarly discussion is available at:

https://en.wikipedia.org/wiki/Computus

Robert Valentino · Jan 1, 2020

1.5 Added Cinco De Mayo has become very popular.

My wife's suggestion

emexes · Jan 2, 2020

WhenIs_ValentinOsDay ?

Is that same as Valentine's Day ? Or your wedding anniversary?

WhenIs_VetransDay ?

Is that Veterans Day ? I feel like that is same as Rememberance Day here (Australia, and rest of British Commonwealth, maybe even Canada too).

If you are looking to standardize the naming of the holidays, perhaps use Wikipedia.

Eg, use SaintPatricksDay instead of SaintPaddysDay.

Or somehow link with www.timeanddate.com, they're pretty good.

Robert Valentino · Jan 2, 2020

Fixed Veterans misspelling. WOW you would think as a vet I could spell it.

As I said in the 1st post. I came across these Excel formulas for dates and thought I was interesting. Wasn't trying to do anything else but share.

As for ValentinOsDay. My last name is Valentino and my Mom always called it ValentinO's day (Always with the big O).
Later in life I moved from NY to Virginia and actually live the town of Valentines You have any problems with that it's just a 1 keystroke fix.

As for SaintPattysDay. My wife's name is Patricia or Patty and after 43+ years of living with me she should be sainted (is that a word).

AS for holidays, I remember 20 years ago when I was working that to me a Holiday was when I got the day off from work. So about 75% of these don't qualify, but for my LED Strip light display they do.

Happy New Year and Enjoy

William Lancee · Jan 2, 2020

@emexes suggestion of

www.timeanddate.com

was fantastic. I looked at it carefully. You can set it to any area of the world and presto, holidays are defined for any year.

emexes · Jan 3, 2020

Robert Valentino said:
As for ValentinOsDay. My last name is Valentino and my Mom always called it ValentinO's day (Always with the big O).

I like your rationale better. Now I'm going to be thinking of you every February 14th :-/

Did you ever find out, why the capital O?

As for SaintPattysDay. My wife's name is Patricia or Patty and after 43+ years of living with me she should be sainted

Lol. And if that is also your marriage anniversary: perfect.

Philip Chatzigeorgiadis · Jan 3, 2020

Cool.

Here is a snippet for Orthodox Easter calculation (results checked until 2070):

B4X:

#Region WhenIs_OrthodoxEasterDay
Public    Sub WhenIs_OrthodoxEasterDay(ForYear As Int) As THolidayIs

    Dim HolidayIs As THolidayIs
    HolidayIs.Initialize
    HolidayIs.IsValid    = True
                       
    Dim startdate As Long = DateTime.DateParse("04/01/" & ForYear)
       
    Dim E As Int =((11*((ForYear-2) Mod 19)) Mod 30)
       
    Dim basedate As Long
    If E>23 Then
        basedate=DateTime.Add(startdate,0,0,56-E)  
    Else
        basedate=DateTime.Add(startdate,0,0,25-E)      
    End If
   
    Dim dow As Int =DateTime.GetDayOfWeek(basedate)
   
    Dim OrthEaster As Long
   
    If basedate > DateTime.DateParse("05/01/" & ForYear) And dow=1 Then
        OrthEaster= basedate
    Else
        OrthEaster =DateTime.Add(basedate,0,0,8-dow)
    End If
                   
    HolidayIs.Month        = DateTime.GetMonth(OrthEaster)
    HolidayIs.Day        = DateTime.GetDayOfMonth(OrthEaster)
    HolidayIs.Year        = DateTime.GetYear(OrthEaster)
    HolidayIs.DayOfWeek    = DateTime.GetDayOfWeek(OrthEaster)

    Log("            Orthodox Easter Day Is " &NumberFormat2(HolidayIs.Month, 2, 0, 0, False) &"/" &NumberFormat2(HolidayIs.Day, 2, 0, 0, False) &"/" &NumberFormat2(HolidayIs.Year, 4, 0, 0, False) &"  -  " &DEFINE_DaysOfWeek(HolidayIs.DayOfWeek))
           
    Return HolidayIs
End Sub
#end region

B4J Code Snippet B4X - cHolidays - Determine when a certain holiday is

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William Lancee

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Robert Valentino

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LucaMs

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William Lancee

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derez

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rabbitBUSH

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William Lancee

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Robert Valentino

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emexes

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Robert Valentino

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William Lancee

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emexes

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Philip Chatzigeorgiadis

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