How can I get a week number in access - ms-access

Question

I've tried this but it returns text15 = 09/12/2020 Result = 2eek, I actually need week 2.
=Format(DatePart("ww",[Text15])-DatePart("ww",DateSerial(Year([Text15]),Month([Text15]),1))+1,"Week ")

Answer 1

you are almost there, try this:
= "Week " & (DatePart("ww",[Text15])-DatePart("ww",DateSerial(Year([Text15]),Month([Text15]),1))) + 1
or this:
="Week " & Abs(Int(-DatePart("d",[Text15])/7))

Answer 2

You can use a method similar to the ISO 8601 numbering of weeks:
' Calculates the "weeknumber of the month" for a date.
' The value will be between 1 and 5.
'
' Numbering is similar to the ISO 8601 numbering having Monday
' as the first day of the week and the first week beginning
' with Thursday or later as week number 1.
' Thus, the first day of a month may belong to the last week
' of the previous month, having a week number of 4 or 5.
'
' 2020-09-23. Gustav Brock, Cactus Data ApS, CPH.
'
Public Function WeekOfMonth( _
ByVal Date1 As Date) _
As Integer
Dim ThursdayInWeek As Date
Dim FirstThursday As Date
Dim WeekNumber As Integer
ThursdayInWeek = DateWeekdayInWeek(Date1, vbThursday, vbMonday)
FirstThursday = DateWeekdayInMonth(ThursdayInWeek, 1, vbThursday)
WeekNumber = 1 + DateDiff("ww", FirstThursday, Date1, vbMonday)
WeekOfMonth = WeekNumber
End Function
As you can see, a supporting function is used:
Option Explicit
Public Const DaysPerWeek As Long = 7
Public Const MaxWeekdayCountInMonth As Integer = 5
' Calculates the "weeknumber of the month" for a date.
' The value will be between 1 and 5.
'
' Numbering is similar to the ISO 8601 numbering having Monday
' as the first day of the week and the first week beginning
' with Thursday or later as week number 1.
' Thus, the first day of a month may belong to the last week
' of the previous month, having a week number of 4 or 5.
'
' 2020-09-23. Gustav Brock, Cactus Data ApS, CPH.
'
Public Function WeekOfMonth( _
ByVal Date1 As Date) _
As Integer
Dim ThursdayInWeek As Date
Dim FirstThursday As Date
Dim WeekNumber As Integer
ThursdayInWeek = DateWeekdayInWeek(Date1, vbThursday)
FirstThursday = DateWeekdayInMonth(ThursdayInWeek, 1, vbThursday)
WeekNumber = 1 + DateDiff("ww", FirstThursday, Date1, vbMonday)
WeekOfMonth = WeekNumber
End Function
' Calculates the date of DayOfWeek in the week of DateInWeek.
' By default, the returned date is the first day in the week
' as defined by the current Windows settings.
'
' Optionally, parameter DayOfWeek can be specified to return
' any other weekday of the week.
' Further, parameter FirstDayOfWeek can be specified to select
' any other weekday as the first weekday of a week.
'
' Limitation:
' For the first and the last week of the range of Date, some
' combinations of DayOfWeek and FirstDayOfWeek that would result
' in dates outside the range of Date, will raise an overflow error.
'
' 2017-05-03. Gustav Brock, Cactus Data ApS, CPH.
'
Public Function DateWeekdayInWeek( _
ByVal DateInWeek As Date, _
Optional ByVal DayOfWeek As VbDayOfWeek = VbDayOfWeek.vbUseSystemDayOfWeek, _
Optional ByVal FirstDayOfWeek As VbDayOfWeek = VbDayOfWeek.vbUseSystemDayOfWeek) _
As Date
Dim DayInWeek As VbDayOfWeek
Dim OffsetZero As Integer
Dim OffsetFind As Integer
Dim ResultDate As Date
' Find the date of DayOfWeek.
DayInWeek = Weekday(DateInWeek)
' Find the offset of the weekday of DateInWeek from the first day of the week.
' Will always be <= 0.
OffsetZero = (FirstDayOfWeek - DayInWeek - DaysPerWeek) Mod DaysPerWeek
' Find the offset of DayOfWeek from the first day of the week.
' Will always be >= 0.
OffsetFind = (DayOfWeek - FirstDayOfWeek + DaysPerWeek) Mod DaysPerWeek
' Calculate result date using the sum of the offset parts.
ResultDate = DateAdd("d", OffsetZero + OffsetFind, DateInWeek)
DateWeekdayInWeek = ResultDate
End Function
' Calculates the date of the occurrence of Weekday in the month of DateInMonth.
'
' If Occurrence is 0 or negative, the first occurrence of Weekday in the month is assumed.
' If Occurrence is 5 or larger, the last occurrence of Weekday in the month is assumed.
'
' If Weekday is invalid or not specified, the weekday of DateInMonth is used.
'
' 2019-12-08. Gustav Brock, Cactus Data ApS, CPH.
'
Public Function DateWeekdayInMonth( _
ByVal DateInMonth As Date, _
Optional ByVal Occurrence As Integer, _
Optional ByVal Weekday As VbDayOfWeek = vbUseSystemDayOfWeek) _
As Date
Dim Offset As Integer
Dim Month As Integer
Dim Year As Integer
Dim ResultDate As Date
' Validate Weekday.
Select Case Weekday
Case _
vbMonday, _
vbTuesday, _
vbWednesday, _
vbThursday, _
vbFriday, _
vbSaturday, _
vbSunday
Case Else
' vbUseSystemDayOfWeek, zero, none or invalid value for VbDayOfWeek.
Weekday = VBA.Weekday(DateInMonth)
End Select
' Validate Occurence.
If Occurrence < 1 Then
' Find first occurrence.
Occurrence = 1
ElseIf Occurrence > MaxWeekdayCountInMonth Then
' Find last occurrence.
Occurrence = MaxWeekdayCountInMonth
End If
' Start date.
Month = VBA.Month(DateInMonth)
Year = VBA.Year(DateInMonth)
ResultDate = DateSerial(Year, Month, 1)
' Find offset of Weekday from first day of month.
Offset = DaysPerWeek * (Occurrence - 1) + (Weekday - VBA.Weekday(ResultDate) + DaysPerWeek) Mod DaysPerWeek
' Calculate result date.
ResultDate = DateAdd("d", Offset, ResultDate)
If Occurrence = MaxWeekdayCountInMonth Then
' The latest occurrency of Weekday is requested.
' Check if there really is a fifth occurrence of Weekday in this month.
If VBA.Month(ResultDate) <> Month Then
' There are only four occurrencies of Weekday in this month.
' Return the fourth as the latest.
ResultDate = DateAdd("d", -DaysPerWeek, ResultDate)
End If
End If
DateWeekdayInMonth = ResultDate
End Function
Watch an example output here.