If you insist on wanting to "change the property name (which I personally think is a TERRIBLE idea), just create a couple of getter/setter extension method that does what you want:
public static int MyRenamedProperty(this MyObject obj)
{
return obj.DAY10;
}
public static void MyRenamedProperty(this MyObject obj, int value)
{
obj.DAY10 = value;
}
Note that this is just a suggestion, and may or may not represent your best option, and that I don't care either way.
EDIT (2022.6.10) -----------------
I'm not sure why this was voted down, or why it took almost 4 years to do it, but what-the-f*ck-ever...