I'm not quite understanding what you want to accomplish.  Could you type out a little example of what you are describing?

I will present what I would like to achieve on an example:
I have 4 records with assigned dates in a continuous form e.g.
1 - 2021/1/1
2 - 2021/1/10
1 - 2022/1/3
3 - 2021/1/7

After entering the date, e.g. 2021/1/6, I would like Access to reassign the number of each entered date and finally it looked like this:
1 - 2021/1/1
2 - 2021/1/6
3 - 2021/1/10
1 - 2022/1/3
4 - 2021/1/7

What is the relationship between the number and the date?  If the numbers represent the order for sorting the dates, why does Jan 10th 2021 come before Jan 7th 2021?

Like Scott and Kevin said, we'd need to know more about your rules. It looks like the count restarts with a new year, but I don't get how you're sorting the dates inside a year.

In the example I gave, there is no relationship between the date and the number, I strive to ensure that access:
- at the beginning of the year, it assigned a number to the entered date starting from 1,
- after entering the date, it sorted all entered dates from the smallest to the largest in a given calendar year and then assigned a number to each entered date, starting from assigning a number. 1 the earliest date in that particular calendar year

Hi Pawel, if you want to store these numbers in the same table that has the dates, then you may use VBA to create a Recordset with your dates sorted, then loop the Recordset to store the numbers.  The sample code below stores ascending-ordered integers for ascending-ordered dates:

    Dim r As Recordset, i As Integer
    Set r = CurrentDB.OpenRecordset("SELECT MyNum, MyDate FROM MyTable ORDER BY MyDate")
    r.MoveFirst
    i = 1
    Do While Not r.EOF
        r.Edit
        r!MyNum = i
        r.Update
        i = i + 1
        r.MoveNext
    Loop
    r.Close

Thank you very much for your support and your time - everything is working fine.