How to make a query not from a table?

Question

PostgreSQL

You need to select dates with an interval of a month, with a condition, for example, for the last 6 months or, for example, for 2015-2016.
Can this be done at all if there is no data table? You just need to select dates with some condition, it is not clear what to write in from and what to apply the condition to

Answer 1

select 
current_date - interval '1 month' * s
from 
generate_series(0, 5) s