# Android Question[Solved] Calculate Easter Day

#### asales

##### Well-Known Member
I found these functions (in VB) that calculates easter day, but I could not convert to B4A (I tried but don't worked):
http://www.cpearson.com/excel/easter.aspx
http://www.codeproject.com/Tips/6630/Computing-Easter-Date-VB-Function

I tried to convert this function made in Delphi...

B4X:
``````function GetGoldenNumber (const Year: Word): Integer;
begin
Result := Year mod 19 + 1;
End;

function GetEasterSunday (const Year: Word): TDateTime;
var
C, I, J, H, G, L: Integer;
D, M: Word;
begin
G := GetGoldenNumber (Year) - 1;
C := Year div 100;
H := (C - C div 4 - (8 * C + 13) div 25 + 19 * G + 15) mod 30;
I := H - (H div 28) * (1 - (H div 28) * (29 div (H + 1))*((21 - G) div 11));
J := (Year + Year div 4 + I + 2 - C + C div 4) mod 7;

L := I - J;
M := 3 + (L + 40) div 44;
D := L + 28 - 31 * (M div 4);
Result := EncodeDate (Year, M, D);
End;``````
to this:

B4X:
``````Sub GetGoldenNumber (Year As Long) As Int
Return Year Mod 19 + 1
End Sub

Sub GetEasterSunday (Year As Long) As Long
Dim C, I, J, H, G, L As Int
Dim D, M As Long

G = GetGoldenNumber(Year) - 1
C = Year / 100
H = (C - C / 4 - (8 * C + 13) / 25 + 19 * G + 15) Mod 30
I = H - (H / 28) * (1 - (H / 28) * (29 / (H + 1))*((21 - G) / 11))
J = (Year + Year / 4 + I + 2 - C + C / 4) Mod 7

L = I - J
M = 3 + (L + 40) / 44
D = L + 28 - 31 * (M / 4)

Return DateTime.DateParse(M & "/" & D & "/" & Year)
End Sub

Label1.Text = DateTime.Date(GetEasterSunday(EditText1.Text))``````
but did not work too.

The easter sunday in 2015 is April 5 and in 2016 is March 27.

I appreciate any help to make this function works.

#### sorex

##### Expert
works fine here for 2015, 2016 is wrong tho (3/3)

#### asales

##### Well-Known Member
works fine here for 2015, 2016 is wrong tho (3/3)
It's really strange.

I tried several dates (Easter = Páscoa):
http://www.inf.ufrgs.br/~cabral/tabela_pascoa.html

Did not work in 2013, 2016, 2021 (in Delphi works fine).

Delphi function returns:
03/31/2013 (correct)
03/27/2016 (correct)

Basic function returns:
03/07/2013 (incorrect)
03/03/2016 (incorrect)

#### DonManfred

##### Expert
NO B4A-Code(!)... Just the info about the calculation to check it (found here)
B4X:
``````  a = J Mod 19
b = J Mod 4
c = J Mod 7
d = (19 * a + 24) Mod 30
e = (2 * b + 4 * c + 6 * d + 5) Mod 7
OT = 22 + d + e
OM = 3
If OT > 31 Then
OT = d + e - 9
OM = 4
End If
If OT = 26 And OM = 4 Then
OT = 19
End If
If OT = 25 And OM = 4 And d = 28 And e = 6 And a > 10 Then
OT = 18
End If``````
Where
J= Number of the year
OM= Month of the Easter Sunday
OT= Day of the Easter Sunday in this month

Original from: Peter Wünsche --- peter.wuensche@ktheo.uni-bamberg.de --- 25.07.95

• asales

#### sorex

##### Expert
remove that goldyear sub and use this instead

B4X:
``````Sub GetEasterSunday (Year As Long) As String
Dim C, I, J, H, G, K,L,N As Int
Dim D, M As Long
G = Year Mod 19
C = Year/100
H = ((C - (C / 4) - (8 * C + 13) / 25) + 19 * G + 15) Mod 30
I = H - (H / 28) * (1 - (H / 28) * (29 / (H + 1))*((21 - G) / 11))
J = (Year + (Year / 4) + I + 2 - C + (C / 4)) Mod 7
L = I - J
M = 3 + ((L + 40) / 44)
D = L + 28 - 31 * Floor(M / 4)
Return (M & "/" & D & "/" & Year)
End Sub``````
Log( GetEasterSunday(2015) )
Log( GetEasterSunday(2016) )

outputs

** Activity (main) Resume **
** Activity (main) Pause, UserClosed = true **
** Activity (main) Create, isFirst = true **
4/5/2015
3/27/2016
** Activity (main) Resume **

• Kapelis and asales

#### DonManfred

##### Expert
nice. A great plus would be if the sub returns a correct datetime value (long). Just a thought... I dont need it

#### sorex

##### Expert
it did in the original but I didn't see the point of it as you want to display it as text anyway, not?

#### asales

##### Well-Known Member
Thanks DonManfred and Sorex.
Both solutions worked.

#### sorex

##### Expert
oh you mean to combine it with dateformat so that you get dd/mm/yyyy for us euros instead?

#### NJDude

##### Expert
A slightly enhanced version of Sorex's code:
B4X:
``````'Format: L = Long date
Sub GetEasterSunday(Year As Long, Format As String) As String

Private C, I, J, H, G, L As Int
Private D, M As Long
Private Month() As String

Month = Array As String("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")

G = Year Mod 19
C = Year/100
H = ((C - (C / 4) - (8 * C + 13) / 25) + 19 * G + 15) Mod 30
I = H - (H / 28) * (1 - (H / 28) * (29 / (H + 1))*((21 - G) / 11))
J = (Year + (Year / 4) + I + 2 - C + (C / 4)) Mod 7
L = I - J
M = 3 + ((L + 40) / 44)
D = L + 28 - 31 * Floor(M / 4)

If Format.ToUpperCase = "L" Then

Return (Month(M - 1) & " " & D & ", " & Year)

Else

Return (M & "/" & D & "/" & Year)

End If

End Sub``````

• asales

#### Rick Harris

##### Well-Known Member
Here is a complete B4A project that not only calculates first Easter day, but many more festive days with an annually changing date:
B4X:
``````#Region  Project Attributes
#ApplicationLabel: DSH electronics Festive Days calculator
#VersionCode: 1
#VersionName:
'SupportedOrientations possible values: unspecified, landscape or portrait.
#SupportedOrientations: unspecified
#CanInstallToExternalStorage: False
#End Region

#Region  Activity Attributes
#FullScreen: False
#IncludeTitle: True
#End Region

Sub Process_Globals
End Sub

Sub Globals
End Sub

Sub Activity_Create(FirstTime As Boolean)
GetFestiveDay("First Easter Day", 2015,0)    'First Easter Day
GetFestiveDay("Second Easter Day",2015,1)    'Second Easter Day
GetFestiveDay("Holy Saturday",2015,-1)       'Holy Saturday
GetFestiveDay("Good Friday",2015,-2)         'Good Friday
GetFestiveDay("White Thursday",2015,-3)      'White Thursday
GetFestiveDay("Ascension Day",2015,39)       'Ascension Day
GetFestiveDay("Whitsun SunDay",2015,49)      'Whitsun SunDay
GetFestiveDay("Whitsun Monday",2015,50)      'Whitsun Monday
GetFestiveDay("Trinity day",2015,56)         'Trinity day
GetFestiveDay("Sacrements day",2015,59)      'Sacrements day
End Sub

Sub Activity_Resume
End Sub

Sub Activity_Pause (UserClosed As Boolean)
End Sub

Sub GetFestiveDay (Descript As String, Year As Long, Day As Long) As String
Dim C, I, J, H, G, L As Int
Dim D, M As Long
Dim D1, M1 As String
Dim WDay As Int
Dim ETicks1 As Long
Dim EDate1 As String
Dim WeekDay(8) As String
WeekDay(1) = "Sun. "
WeekDay(2) = "Mon. "
WeekDay(3) = "Tue. "
WeekDay(4) = "Wed. "
WeekDay(5) = "Thu. "
WeekDay(6) = "Fri. "
WeekDay(7) = "Sat. "

G = Year Mod 19
C = Year/100
H = ((C - (C / 4) - (8 * C + 13) / 25) + 19 * G + 15) Mod 30
I = H - (H / 28) * (1 - (H / 28) * (29 / (H + 1))*((21 - G) / 11))
J = (Year + (Year / 4) + I + 2 - C + (C / 4)) Mod 7
L = I - J
M = 3 + ((L + 40) / 44)
D = L + 28 - 31 * Floor(M / 4)
M1=M
D1=D
If M1.Length = 1 Then M1 = "0" & M1
If D1.Length = 1 Then D1 = "0" & D1
DateTime.DateFormat = "dd/MM/yyyy"
ETicks1 = DateTime.DateParse(D1 & "/" & M1 & "/" & Year)
EDate1 = DateTime.Date(ETicks1+(Day * 86400000))
WDay = DateTime.GetDayOfWeek(ETicks1+(Day * 86400000))
Log(Descript & "= " & WeekDay(WDay) & EDate1)
End Sub``````

• asales