Will give you the number of repository that did not receive any commit within the last year

bigquery-github-1.sql

SELECT COUNT(sub_github.repo_name) 
FROM (
    SELECT i.repo_name, MAX(committer.time_sec) as MaxDate
    FROM [bigquery-public-data:github_repos.commits] AS i
    GROUP BY i.repo_name
) AS sub_github
WHERE sub_github.MaxDate < ((NOW() / 1000000) - 31622400)