by Garnet Tozer (1 Submission)
Category: Math/Dates
Compatability: Visual Basic 3.0
Difficulty: Unknown Difficulty
Originally Published: Wed 22nd November 2000
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
Mathematically calculate the day of the week.
VBcoders
Dim DOW As Integer
DOW = DayOfWeek(2000, 11, 22) ' November 22, 2000
Select Case DOW
Case 0:
Print "Sunday"
Case 1:
Print "Monday"
Case 2:
Print "Tuesday"
Case 3:
Print "Wednesday"
Case 4:
Print "Thursday"
Case 5:
Print "Friday"
Case 6
Print "Saturday"
Case Else
Print "Error"
End Select
End Sub
Private Function DayOfWeek(y As Integer, m As Integer, d As Integer)
' Programmatically calculate the day of the week from a given date.
' DOW = ([23m/9] + d + 4 + z + [z/4] - [z/100] + [z/400] - 2 (if m>=3)) mod 7
'
' y is the 4 digit year
' m is the month
' d is the day.
' z = y - 1 (if m < 3)
' = y (if m >= 3)
' A mod B means take the reminder of A / B.
'
' Sunday = 0, Monday = 1, etc.
'
If m < 3 Then
y = y - 1
Else
y = y - 2
End If
DayOfWeek = ((23 * m / 9 + d + 4 + y + (y / 4) - (y / 100) + (y / 400)) Mod 7)
End Function
