Can't rename columns in PostgreSQL views with CREATE OR REPLACE
I can reproduce your error ... in my case, I created a column first as 'date' then as 'x' (was trying to see if it was an issue with a reserved word; it wasn't:

ERROR:  cannot change name of view column "date" to "x"


If you issue a drop view first, it'll let you re-create the view with a changed name.  I have no idea why create or replace won't do it.



Clarification by Colin 't Hart:

The documentation for CREATE VIEW explains it pretty well, I think:


  The new query must generate the same columns that were generated by the existing view query (that is, the same column names in the same order and with the same data types), but it may add additional columns to the end of the list.