Anybody knows the problem of this code?

My code is this:
shared function dataFisica( byVal data as Date ) as Date
If data='01/01/1900' Then
return ' '
Else
return data
End If
end function
And the reporting services do an error in line 1.
Try using double quotes instead of single quotes

function dataFisica( byVal data as Date ) as Date
If data="01/01/1900" Then
return ""
Else
return data
End If
end function