This is how I ended up doing it
INSERT INTO web_stats (date_created)
SELECT DATE('2011-08-20')+x.id
FROM generate_series(0,521) AS x(id);
Where 2011-08-20 is the date the application went live, and 521 is the number of days from now until then
This creates the empty table so that I can use the date_created field to populate the other fields using UPDATE statements
Maybe not the most efficient method but it works