Hi @Anonymous,
Do you mean date format like 2023/week 15?
Could you please tell me that how you define two values in the Datuminput? Two characters? How you convert two characters into YY/WW?
Actually, in Power Apps, to convert date into YY, we used to use the "yy".
If you just want to add a year to the TextInput where inputs weeknumber, I think you should set the OnChange property of the Datuminput as below:
If(Len(Datuminput.Text) = 2,Set(DateFormat,Text(Today(),"yy")&Char(47)&Datuminput.Text))
Then you need to apply this variable to the Default property of the Datuminput:
DateFormat
What's more, to trigger the variable in the OnChange property, you need to click anywhere outside of the Datuminput, so that the variable will be triggered.