Android Question Parsing a date with complex conditions using AI

Sub Process_Globals
    Private Prefixes As List = Array As String("ABT", "CAL", "EST", "AFT", "BEF", "BET", "FROM")
    Private PrefixesWithInfix As List = Array As String("BET", "FROM")
    Private Infixes As List = Array As String("AND", "TO")
    Type MyDate (Prefix As String, Day As String, Month As String, Year As String, Text As String)
End Sub

Sub AppStart (Args() As String)
    DateTime.DateFormat = "dd MMM yyyy"
    ParseText("BET 1 JAN 1852 AND 31 DEC 1852")
    ParseText("ABT 3 SEP 1852") ' Note: SEP is not parseable in UK english locale
    ParseText("FROM 31 DEC 1852")
    ParseText("FROM 1 FEB 2025 AND 30 NOV 2025")
    ParseText("BET 1 FEB 2026 TO 30 NOV 2026")
    ParseText("FROM 1 FEB 2025 TO 30 NOV 2025")
    ParseText("BET 1 FEB 2026 AND 30 NOV 2026")
End Sub

Private Sub ParseText (Text As String)
    Dim Date1, Date2 As MyDate
    Dim Prefix As String
    Dim Infix As String = GetInfix(Text)
    If Infix <> "" Then
        Dim DateParts() As String = Regex.Split($" ${Infix} "$, Text)
        Prefix = GetPrefix(DateParts(0))
      
        ' Checking matching prefix to infix with simple if-else
        If Prefix = "FROM" And Infix <> "TO" Then
            Log("Invalid date! " & Text)
            Return
        End If
        If Prefix = "BET" And Infix <> "AND" Then
            Log("Invalid date! " & Text)
            Return
        End If
      
        DateParts(0) = DateParts(0).SubString(Prefix.Length + 1)
        Date1 = ParseDate(Prefix, DateParts(0))
        Log($"Date1=(${Date1.Prefix}, ${Date1.Day}, ${Date1.Month}, ${Date1.Year}, ${Date1.Text})"$)
      
        Date2 = ParseDate(Infix, DateParts(1))
        Log($"Date2=(${Date2.Prefix}, ${Date2.Day}, ${Date2.Month}, ${Date2.Year}, ${Date2.Text})"$)
    Else     
        Prefix = GetPrefix(Text)
        If PrefixesWithInfix.IndexOf(Prefix) > -1 Then
            Log("Invalid date! " & Text)
            Return
        End If
        Dim DateParts() As String = Array As String(Text.SubString(Prefix.Length + 1))
        Date1 = ParseDate(Prefix, DateParts(0))
        If Date1.IsInitialized Then
            Log($"Date1=(${Date1.Prefix}, ${Date1.Day}, ${Date1.Month}, ${Date1.Year}, ${Date1.Text})"$)
        Else
            Log("Invalid date! " & Text)
        End If
    End If
End Sub

Private Sub GetInfix (Text As String) As String
    For Each Infix As String In Infixes
        If Text.Contains($" ${Infix} "$) Then
            Return Infix
        End If
    Next
    Return ""
End Sub

Private Sub GetPrefix (Text As String) As String
    For Each Prefix As String In Prefixes
        If Text.StartsWith(Prefix) Then
            Return Prefix
        End If
    Next
    Return ""
End Sub

Private Sub ParseDate (Fix As String, DateString As String) As MyDate
    Dim TestDate As MyDate
    Try
        ' Fix Sept
        DateString = DateString.Replace(" SEP ", " SEPT ")
        Dim Ticks As Long =  DateTime.DateParse(DateString)
        DateString = DateString.Replace(" SEPT ", " SEP ")
        Return CreateMyDate(Fix, GetDay(Ticks), GetMonth(Ticks), GetYear(Ticks), DateString)
    Catch
        Log(LastException)
        Return TestDate
    End Try
End Sub

Private Sub GetDay (DateTicks As Long) As String
    Return DateTime.GetDayOfMonth(DateTicks)
End Sub

Private Sub GetMonth (DateTicks As Long) As String
    'Return DateTime.GetMonth(DateTicks)
    Return DateUtils.GetMonthName(DateTicks).SubString2(0, 3).ToUpperCase
End Sub

Private Sub GetYear (DateTicks As Long) As String
    Return DateTime.GetYear(DateTicks)
End Sub

Public Sub CreateMyDate (Prefix As String, Day As String, Month As String, Year As String, Text As String) As MyDate
    Dim t1 As MyDate
    t1.Initialize
    t1.Prefix = Prefix
    t1.Day = Day
    t1.Month = Month
    t1.Year = Year
    t1.Text = Text
    Return t1
End Sub