Hi @akbarmahfuzalam ,
See the Solution for your requirement.
Hope this will help you to achieve your requirement.
Code below -
If(Value(Text(DatePicker5.SelectedDate,"[$-en-US]d"))>=1 && Value(Text(DatePicker5.SelectedDate,"[$-en-US]d"))<=15,DateValue(Text(Text(DatePicker5.SelectedDate,"[$-en-US]mm")&"/"&"15/"&Text(DatePicker5.SelectedDate,"[$-en-US]yyyy"))),If(Value(Text(DatePicker5.SelectedDate,"[$-en-US]d"))>=16 && Value(Text(DatePicker5.SelectedDate,"[$-en-US]d"))<=31,DateAdd( DateAdd( Date(Year(DatePicker5.SelectedDate), Month(DatePicker5.SelectedDate), 1), 1, Months), -1, Days)))

Thanks,
Vijay
Please click "Accept as Solution" if my post answered your question so that others may find it more quickly. If you found this post helpful consider giving it a "Thumbs Up."-Vijay