These functions look for a specific Day Of Week near a date. E.g. What is first Thursday On or After 1 Jan 2000 or What is Nearest Sunday to 7 June 2025.
 

Private Shared Function DayOfWeek_Near_Date(DoW As DayOfWeek, Rule1 As NearestRule, dat As Date) As Date
 Dim KeyDate As Date
 Select Case Rule1
  Case NearestRule.Before_Date : KeyDate = dat.AddDays(-7)
  Case NearestRule.OnOrBefore_Date : KeyDate = dat.AddDays(-6)
  Case NearestRule.NearestTo_Date : KeyDate = dat.AddDays(-3)
  Case NearestRule.OnOrAfter_Date : KeyDate = dat
  Case NearestRule.After_Date : KeyDate = dat.AddDays(1)
 End Select
 Return KeyDate.AddDays((CInt(DoW) + 7 - CInt(KeyDate.DayOfWeek)) Mod 7)
End Function

Private Enum NearestRule
 Before_Date
 OnOrBefore_Date
 NearestTo_Date
 OnOrAfter_Date
 After_Date
End Enum
  

 
Variations of this function can be useful when calculating Public Holiday Dates. E.g. In the UK, the date of any Public Holiday that would normally fall on a Weekend is adjusted to the first Weekday after the normal date.
 

Private Shared Function WeekDay_OnOrAfter_Date(dat As Date) As Date
 Select Case dat.DayOfWeek
  Case DayOfWeek.Saturday : dat = dat.AddDays(2)
  Case DayOfWeek.Sunday : dat = dat.AddDays(1)
 End Select
 Return dat
End Function

Private Function WeekDay_OnOrBefore_Date(dat As Date) As Date
 Select Case dat.DayOfWeek
  Case DayOfWeek.Saturday : dat = dat.AddDays(-1)
  Case DayOfWeek.Sunday : dat = dat.AddDays(-2)
 End Select
 Return dat
End Function

Private Function Weekend_OnOrAfter_Date(dat As Date) As Date
 Select Case dat.DayOfWeek
  Case DayOfWeek.Monday : dat = dat.AddDays(5)
  Case DayOfWeek.Tuesday : dat = dat.AddDays(4)
  Case DayOfWeek.Wednesday : dat = dat.AddDays(3)
  Case DayOfWeek.Thursday : dat = dat.AddDays(2)
  Case DayOfWeek.Friday : dat = dat.AddDays(1)
 End Select
 Return dat
End Function

Private Function Weekend_OnOrBefore_Date(dat As Date) As Date
 Select Case dat.DayOfWeek
  Case DayOfWeek.Monday : dat = dat.AddDays(-1)
  Case DayOfWeek.Tuesday : dat = dat.AddDays(-2)
  Case DayOfWeek.Wednesday : dat = dat.AddDays(-3)
  Case DayOfWeek.Thursday : dat = dat.AddDays(-4)
  Case DayOfWeek.Friday : dat = dat.AddDays(-5)
 End Select
 Return dat
End Function
  

 

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