The code works; the problem is in the processing. I feel like the code can further improved and I believe the answer is Arrays however, my knowledge is very limited. Here, I loop through ~ 1000 columns. Each column has a start and end date; which will span from 1 day to 20 days, averaging ~ 3-5 days for each column. Upwards of 5000 lines are moved through and it shows in the speed of return. I will be adding If statements and I feel that if I add too much more where I am at that the program will crash. 
    
I am hoping to speed it up. I believe arrays will do this however, the only array I use in here is borrowed from SO (thank you to all who answer questions, you have helped build this code, whether it was just a tip or a block of code pulled and revamped). Thank you for any help you are willing to provide, even if it is just a good reference that will help me in improving it further.

    
    [Tab Month Tracker]: https://ibb.co/cJx0f9v
    [Raw Data Columns]: https://ibb.co/1J5gHbf
    [Tabs Example]: https://ibb.co/8m6ymY4

    
    'Function to return array for dates between Start Date and End Date
    Function GetDatesRange(dateStart As Date, dateEnd As Date) As Collection
    Dim dates As New Collection
    Dim currentDate As Date
    currentDate = dateStart
    Do While currentDate <= dateEnd
    
        dates.Add currentDate
        currentDate = DateAdd("d", 1, currentDate)
    Loop
    Set GetDatesRange = dates
    End Function


    
    'Sub to move raw data into predictable format
    Sub Program()

    Application.ScreenUpdating = False

    Dim dateStartCell As Range, dateEndCell As Range, StartDate As Range, Cell As Range
    Dim allDates As Collection
    Dim currentDateSter As Variant
    Dim currentDate As Date
    Dim TestDate As Integer

    Dim NextRow As Long
    Dim AdvRow As Long

    Dim Facility As String
    Dim Unit As String
    Dim TheDay As String
    Dim TheUnit As String
    Dim Pax As String

    Dim Test1 As Boolean
    Dim Test2 As Boolean

    Set StartDate = Range("E2:E1000")

    NextRow = 2

    Sheets("Raw").Activate

    'Evaluating Each Date in Range
    For Each Cell In StartDate

    Set dateStartCell = Range("E" & NextRow)
    Set dateEndCell = Range("G" & NextRow)
    Set allDates = GetDatesRange(dateStartCell.Value, dateEndCell.Value)
    
    Facility = Cells(NextRow, 3)
    Unit = Cells(NextRow, 2)
    Pax = Cells(NextRow, 12)
        'Evaluating if the date and name already exist
        For Each currentDateSter In allDates
            currentDate = CDate(currentDateSter)
            Sheets(MonthName(Month(currentDate), True) & Year(currentDate)).Activate
            
            
            AdvRow = 3
            PropRow = Empty
            Test1 = False
            Test2 = False
            'evaluating if the date and name already exists if it does, and determines row for data entry
            'eventually end up writing over data if it already exists however, column C has 125 unique possibilities
            'that will fill another column in the month tabs
            Do
            AdvRow = AdvRow + 1
            PropRow = AdvRow
                            
            TheDay = Cells(AdvRow, 1)
            TheUnit = Cells(AdvRow, 2)
                
                If TheDay = Day(currentDate) And TheUnit = Unit Then
                Test1 = True
                Else: Test1 = False
                End If
            
                If TheDay = TheUnit Then
                Test2 = True
                Else: Test2 = False
                End If
        
            Loop Until Test1 = True Or Test2 = True
            
        
        
        Cells(PropRow, 2).Value = Unit
        Cells(PropRow, 1).Value = Day(currentDate)
        Cells(PropRow, 3).Value = Pax
        
        
        
        
        Sheets("Raw").Activate
        
        Next currentDateSter
        
    NextRow = NextRow + 1  
    Next Cell
    Application.ScreenUpdating = True
    End Sub