The order of operations to satisfy a query is determined why the whim of the particular database's query optimizer. A query optimizer tries to product a good "query plan" (set of operations) based on what it can glean from the query and whatever statistics it has on hand about the database (which could include the cardinality of tables and certain distributions of data).
In your case, the answer may depend on whether you have a secondary index on A.date
Query optimization a fairly rich topic. The documentation for whatever database you're using will have a lot more to say about it.
