Subtracting Dates Macro Issue

I have the below code that subtracts a date that I type into B3 (the cell is formatted dd/mm/yyyy) from the date in cell B1 which is todays date. If I have tomorrows date in B3 the result returned is 0 when it should be 1. Why is this?

Sub Test1()

Application.ScreenUpdating = False

With ThisWorkbook.Worksheets("Data") 

 .Range("B1").Formula = "=NOW()"
 .Range("B1").NumberFormat = "dd/mm/yyyy"
  
.Range("X3").Formula = "=B3-$B$1"

Application.ScreenUpdating = True
End With
End Sub